From 7c9fabf7150d6031d95cc0220c091405ce77367e Mon Sep 17 00:00:00 2001
From: Yvonne Pan <103622026+yvonnep165@users.noreply.github.com>
Date: Tue, 24 Mar 2026 17:14:07 -0400
Subject: [PATCH] Refactor the parameters for timestamp expressions and change
 all timegranularity value to lowercase

---
 .../firestore/api-report/firestore.api.md     |  42 +++----
 .../firestore/dev/src/pipelines/expression.ts | 117 ++++--------------
 handwritten/firestore/types/firestore.d.ts    | 116 ++++-------------
 3 files changed, 63 insertions(+), 212 deletions(-)

diff --git a/handwritten/firestore/api-report/firestore.api.md b/handwritten/firestore/api-report/firestore.api.md
index 78383dbd1d8..6bd66ae03d1 100644
--- a/handwritten/firestore/api-report/firestore.api.md
+++ b/handwritten/firestore/api-report/firestore.api.md
@@ -1137,7 +1137,7 @@ abstract class Expression implements firestore.Pipelines.Expression, HasUserData
     ifError(catchValue: unknown): FunctionExpression;
     isAbsent(): BooleanExpression;
     isError(): BooleanExpression;
-    isType(type: Type): BooleanExpression;
+    isType(type: string): BooleanExpression;
     join(delimiterExpression: Expression): Expression;
     join(delimiter: string): Expression;
     last(): AggregateFunction;
@@ -1206,13 +1206,13 @@ abstract class Expression implements firestore.Pipelines.Expression, HasUserData
     subtract(subtrahend: number): FunctionExpression;
     sum(): AggregateFunction;
     timestampAdd(unit: Expression, amount: Expression): FunctionExpression;
-    timestampAdd(unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day', amount: number): FunctionExpression;
+    timestampAdd(unit: firestore.Pipelines.TimeUnit, amount: number): FunctionExpression;
     timestampDiff(start: Expression, unit: Expression): FunctionExpression;
-    timestampDiff(start: string | Expression, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day'): FunctionExpression;
+    timestampDiff(start: string | Expression, unit: firestore.Pipelines.TimeUnit): FunctionExpression;
     timestampExtract(part: firestore.Pipelines.TimePart, timezone?: string | Expression): FunctionExpression;
     timestampExtract(part: Expression, timezone?: string | Expression): FunctionExpression;
     timestampSubtract(unit: Expression, amount: Expression): FunctionExpression;
-    timestampSubtract(unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day', amount: number): FunctionExpression;
+    timestampSubtract(unit: firestore.Pipelines.TimeUnit, amount: number): FunctionExpression;
     timestampToUnixMicros(): FunctionExpression;
     timestampToUnixMillis(): FunctionExpression;
     timestampToUnixSeconds(): FunctionExpression;
@@ -1418,6 +1418,8 @@ class Firestore implements firestore.Firestore {
     // Warning: (tsdoc-param-tag-with-invalid-name) The @param block should be followed by a valid parameter name: The identifier cannot non-word characters
     // Warning: (tsdoc-param-tag-with-invalid-type) The @param block should not include a JSDoc-style '{type}'
     constructor(settings?: firestore.Settings);
+    // @internal
+    get alwaysUseImplicitOrderBy(): boolean;
     // Warning: (tsdoc-escape-right-brace) The "}" character should be escaped using a backslash to avoid confusion with a TSDoc inline tag
     // Warning: (tsdoc-malformed-inline-tag) Expecting a TSDoc tag starting with "{@"
     batch(): WriteBatch;
@@ -1650,10 +1652,10 @@ function isAbsent(field: string): BooleanExpression;
 function isError(value: Expression): BooleanExpression;
 
 // @beta
-function isType(fieldName: string, type: Type): BooleanExpression;
+function isType(fieldName: string, type: string): BooleanExpression;
 
 // @beta
-function isType(expression: Expression, type: Type): BooleanExpression;
+function isType(expression: Expression, type: string): BooleanExpression;
 
 // @beta
 function join(arrayFieldName: string, delimiter: string): Expression;
@@ -2118,7 +2120,6 @@ declare namespace Pipelines {
         arrayConcat,
         type,
         isType,
-        Type,
         timestampTruncate,
         timestampExtract,
         timestampDiff,
@@ -2360,7 +2361,7 @@ export class Query<AppModelType = firestore.DocumentData, DbModelType extends fi
     // Warning: (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
     //
     // @internal
-    toProto(transactionOrReadTime?: Uint8Array | Timestamp | api.ITransactionOptions, explainOptions?: firestore.ExplainOptions): api.IRunQueryRequest;
+    toProto(transactionOrReadTime?: Uint8Array | Timestamp | api.ITransactionOptions, explainOptions?: firestore.ExplainOptions, forceImplicitOrderBy?: boolean): api.IRunQueryRequest;
     // Warning: (tsdoc-param-tag-with-invalid-type) The @param block should not include a JSDoc-style '{type}'
     // Warning: (tsdoc-param-tag-with-invalid-type) The @param block should not include a JSDoc-style '{type}'
     // Warning: (tsdoc-param-tag-with-invalid-type) The @param block should not include a JSDoc-style '{type}'
@@ -2710,22 +2711,22 @@ export class Timestamp implements firestore.Timestamp {
 function timestampAdd(timestamp: Expression, unit: Expression, amount: Expression): FunctionExpression;
 
 // @beta
-function timestampAdd(timestamp: Expression, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day', amount: number): FunctionExpression;
+function timestampAdd(timestamp: Expression, unit: firestore.Pipelines.TimeUnit, amount: number): FunctionExpression;
 
 // @beta
-function timestampAdd(fieldName: string, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day', amount: number): FunctionExpression;
+function timestampAdd(fieldName: string, unit: firestore.Pipelines.TimeUnit, amount: number): FunctionExpression;
 
 // @beta
-function timestampDiff(endFieldName: string, startFieldName: string, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day' | Expression): FunctionExpression;
+function timestampDiff(endFieldName: string, startFieldName: string, unit: firestore.Pipelines.TimeUnit | Expression): FunctionExpression;
 
 // @beta
-function timestampDiff(endFieldName: string, startExpression: Expression, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day' | Expression): FunctionExpression;
+function timestampDiff(endFieldName: string, startExpression: Expression, unit: firestore.Pipelines.TimeUnit | Expression): FunctionExpression;
 
 // @beta
-function timestampDiff(endExpression: Expression, startFieldName: string, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day' | Expression): FunctionExpression;
+function timestampDiff(endExpression: Expression, startFieldName: string, unit: firestore.Pipelines.TimeUnit | Expression): FunctionExpression;
 
 // @beta
-function timestampDiff(endExpression: Expression, startExpression: Expression, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day' | Expression): FunctionExpression;
+function timestampDiff(endExpression: Expression, startExpression: Expression, unit: firestore.Pipelines.TimeUnit | Expression): FunctionExpression;
 
 // @beta
 function timestampExtract(fieldName: string, part: firestore.Pipelines.TimePart, timezone?: string | Expression): FunctionExpression;
@@ -2743,10 +2744,10 @@ function timestampExtract(timestampExpression: Expression, part: Expression, tim
 function timestampSubtract(timestamp: Expression, unit: Expression, amount: Expression): FunctionExpression;
 
 // @beta
-function timestampSubtract(timestamp: Expression, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day', amount: number): FunctionExpression;
+function timestampSubtract(timestamp: Expression, unit: firestore.Pipelines.TimeUnit, amount: number): FunctionExpression;
 
 // @beta
-function timestampSubtract(fieldName: string, unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day', amount: number): FunctionExpression;
+function timestampSubtract(fieldName: string, unit: firestore.Pipelines.TimeUnit, amount: number): FunctionExpression;
 
 // @beta
 function timestampToUnixMicros(expr: Expression): FunctionExpression;
@@ -2906,9 +2907,6 @@ function trunc(fieldName: string, decimalPlaces: number | Expression): FunctionE
 // @beta
 function trunc(expression: Expression, decimalPlaces: number | Expression): FunctionExpression;
 
-// @beta
-type Type = 'null' | 'array' | 'boolean' | 'bytes' | 'timestamp' | 'geo_point' | 'number' | 'int32' | 'int64' | 'float64' | 'decimal128' | 'map' | 'reference' | 'string' | 'vector' | 'max_key' | 'min_key' | 'object_id' | 'regex' | 'request_timestamp';
-
 // Warning: (tsdoc-escape-right-brace) The "}" character should be escaped using a backslash to avoid confusion with a TSDoc inline tag
 // Warning: (tsdoc-malformed-inline-tag) Expecting a TSDoc tag starting with "{@"
 //
@@ -3148,9 +3146,9 @@ function xor(first: BooleanExpression, second: BooleanExpression, ...additionalC
 // build/types/src/index.d.ts:371:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
 // build/types/src/index.d.ts:378:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
 // build/types/src/index.d.ts:387:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
-// build/types/src/index.d.ts:881:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
-// build/types/src/index.d.ts:900:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
-// build/types/src/index.d.ts:915:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
+// build/types/src/index.d.ts:886:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
+// build/types/src/index.d.ts:905:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
+// build/types/src/index.d.ts:920:8 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
 // build/types/src/path.d.ts:29:4 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
 // build/types/src/path.d.ts:31:4 - (tsdoc-undefined-tag) The TSDoc tag "@class" is not defined in this configuration
 // build/types/src/path.d.ts:146:4 - (tsdoc-undefined-tag) The TSDoc tag "@private" is not defined in this configuration
diff --git a/handwritten/firestore/dev/src/pipelines/expression.ts b/handwritten/firestore/dev/src/pipelines/expression.ts
index a295f604045..2905e4f78e6 100644
--- a/handwritten/firestore/dev/src/pipelines/expression.ts
+++ b/handwritten/firestore/dev/src/pipelines/expression.ts
@@ -2323,18 +2323,11 @@ export abstract class Expression
    * @returns A new `Expression` representing the resulting timestamp.
    */
   timestampAdd(
-    unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+    unit: firestore.Pipelines.TimeUnit,
     amount: number,
   ): FunctionExpression;
   timestampAdd(
-    unit:
-      | Expression
-      | 'microsecond'
-      | 'millisecond'
-      | 'second'
-      | 'minute'
-      | 'hour'
-      | 'day',
+    unit: Expression | firestore.Pipelines.TimeUnit,
     amount: Expression | number,
   ): FunctionExpression {
     return new FunctionExpression('timestamp_add', [
@@ -2375,18 +2368,11 @@ export abstract class Expression
    * @returns A new `Expression` representing the resulting timestamp.
    */
   timestampSubtract(
-    unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+    unit: firestore.Pipelines.TimeUnit,
     amount: number,
   ): FunctionExpression;
   timestampSubtract(
-    unit:
-      | Expression
-      | 'microsecond'
-      | 'millisecond'
-      | 'second'
-      | 'minute'
-      | 'hour'
-      | 'day',
+    unit: Expression | firestore.Pipelines.TimeUnit,
     amount: Expression | number,
   ): FunctionExpression {
     return new FunctionExpression('timestamp_subtract', [
@@ -2428,18 +2414,11 @@ export abstract class Expression
    */
   timestampDiff(
     start: string | Expression,
-    unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+    unit: firestore.Pipelines.TimeUnit,
   ): FunctionExpression;
   timestampDiff(
     start: string | Expression,
-    unit:
-      | 'microsecond'
-      | 'millisecond'
-      | 'second'
-      | 'minute'
-      | 'hour'
-      | 'day'
-      | Expression,
+    unit: Expression | firestore.Pipelines.TimeUnit,
   ): FunctionExpression {
     return new FunctionExpression('timestamp_diff', [
       this,
@@ -2493,8 +2472,7 @@ export abstract class Expression
     part: firestore.Pipelines.TimePart | Expression,
     timezone?: string | Expression,
   ): FunctionExpression {
-    const internalPart = isString(part) ? part.toLowerCase() : part;
-    const args = [this, valueToDefaultExpr(internalPart)];
+    const args = [this, valueToDefaultExpr(part)];
     if (timezone) {
       args.push(valueToDefaultExpr(timezone));
     }
@@ -3123,11 +3101,7 @@ export abstract class Expression
     granularity: firestore.Pipelines.TimeGranularity | Expression,
     timezone?: string | Expression,
   ): FunctionExpression {
-    const internalGranularity = isString(granularity)
-      ? granularity.toLowerCase()
-      : granularity;
-
-    const args = [this, valueToDefaultExpr(internalGranularity)];
+    const args = [this, valueToDefaultExpr(granularity)];
     if (timezone) {
       args.push(valueToDefaultExpr(timezone));
     }
@@ -8501,7 +8475,7 @@ export function timestampAdd(
  */
 export function timestampAdd(
   timestamp: Expression,
-  unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+  unit: firestore.Pipelines.TimeUnit,
   amount: number,
 ): FunctionExpression;
 
@@ -8521,19 +8495,12 @@ export function timestampAdd(
  */
 export function timestampAdd(
   fieldName: string,
-  unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+  unit: firestore.Pipelines.TimeUnit,
   amount: number,
 ): FunctionExpression;
 export function timestampAdd(
   timestamp: Expression | string,
-  unit:
-    | Expression
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day',
+  unit: Expression | firestore.Pipelines.TimeUnit,
   amount: Expression | number,
 ): FunctionExpression {
   const normalizedTimestamp = fieldOrExpression(timestamp);
@@ -8578,7 +8545,7 @@ export function timestampSubtract(
  */
 export function timestampSubtract(
   timestamp: Expression,
-  unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+  unit: firestore.Pipelines.TimeUnit,
   amount: number,
 ): FunctionExpression;
 
@@ -8598,19 +8565,12 @@ export function timestampSubtract(
  */
 export function timestampSubtract(
   fieldName: string,
-  unit: 'microsecond' | 'millisecond' | 'second' | 'minute' | 'hour' | 'day',
+  unit: firestore.Pipelines.TimeUnit,
   amount: number,
 ): FunctionExpression;
 export function timestampSubtract(
   timestamp: Expression | string,
-  unit:
-    | Expression
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day',
+  unit: Expression | firestore.Pipelines.TimeUnit,
   amount: Expression | number,
 ): FunctionExpression {
   const normalizedTimestamp = fieldOrExpression(timestamp);
@@ -9605,7 +9565,7 @@ export function timestampTruncate(
   timezone?: string | Expression,
 ): FunctionExpression {
   const internalGranularity = isString(granularity)
-    ? valueToDefaultExpr(granularity.toLowerCase())
+    ? valueToDefaultExpr(granularity)
     : granularity;
   return fieldOrExpression(fieldNameOrExpression).timestampTruncate(
     internalGranularity,
@@ -9631,14 +9591,7 @@ export function timestampTruncate(
 export function timestampDiff(
   endFieldName: string,
   startFieldName: string,
-  unit:
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day'
-    | Expression,
+  unit: firestore.Pipelines.TimeUnit | Expression,
 ): FunctionExpression;
 
 /**
@@ -9659,14 +9612,7 @@ export function timestampDiff(
 export function timestampDiff(
   endFieldName: string,
   startExpression: Expression,
-  unit:
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day'
-    | Expression,
+  unit: firestore.Pipelines.TimeUnit | Expression,
 ): FunctionExpression;
 
 /**
@@ -9687,14 +9633,7 @@ export function timestampDiff(
 export function timestampDiff(
   endExpression: Expression,
   startFieldName: string,
-  unit:
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day'
-    | Expression,
+  unit: firestore.Pipelines.TimeUnit | Expression,
 ): FunctionExpression;
 
 /**
@@ -9715,26 +9654,12 @@ export function timestampDiff(
 export function timestampDiff(
   endExpression: Expression,
   startExpression: Expression,
-  unit:
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day'
-    | Expression,
+  unit: firestore.Pipelines.TimeUnit | Expression,
 ): FunctionExpression;
 export function timestampDiff(
   endFieldNameOrExpression: string | Expression,
   startFieldNameOrExpression: string | Expression,
-  unit:
-    | 'microsecond'
-    | 'millisecond'
-    | 'second'
-    | 'minute'
-    | 'hour'
-    | 'day'
-    | Expression,
+  unit: firestore.Pipelines.TimeUnit | Expression,
 ): FunctionExpression {
   const normalizedEnd = fieldOrExpression(endFieldNameOrExpression);
   const normalizedStart = fieldOrExpression(startFieldNameOrExpression);
@@ -9839,7 +9764,7 @@ export function timestampExtract(
   timezone?: string | Expression,
 ): FunctionExpression {
   return fieldOrExpression(fieldNameOrExpression).timestampExtract(
-    valueToDefaultExpr(isString(part) ? part.toLowerCase() : part),
+    valueToDefaultExpr(part),
     timezone,
   );
 }
diff --git a/handwritten/firestore/types/firestore.d.ts b/handwritten/firestore/types/firestore.d.ts
index 8cd99823648..7e1d6307ecf 100644
--- a/handwritten/firestore/types/firestore.d.ts
+++ b/handwritten/firestore/types/firestore.d.ts
@@ -4991,16 +4991,7 @@ declare namespace FirebaseFirestore {
        * @param amount The amount of time to add.
        * @returns A new {@code Expression} representing the resulting timestamp.
        */
-      timestampAdd(
-        unit:
-          | 'microsecond'
-          | 'millisecond'
-          | 'second'
-          | 'minute'
-          | 'hour'
-          | 'day',
-        amount: number,
-      ): FunctionExpression;
+      timestampAdd(unit: TimeUnit, amount: number): FunctionExpression;
       /**
        * @beta
        * Creates an expression that subtracts a specified amount of time from this timestamp expression.
@@ -5034,16 +5025,7 @@ declare namespace FirebaseFirestore {
        * @param amount The amount of time to subtract.
        * @returns A new {@code FunctionExpression} representing the resulting timestamp after subtraction.
        */
-      timestampSubtract(
-        unit:
-          | 'microsecond'
-          | 'millisecond'
-          | 'second'
-          | 'minute'
-          | 'hour'
-          | 'day',
-        amount: number,
-      ): FunctionExpression;
+      timestampSubtract(unit: TimeUnit, amount: number): FunctionExpression;
       /**
        * @beta
        * Creates an expression that returns the document ID from a DocumentReference.
@@ -5610,16 +5592,7 @@ declare namespace FirebaseFirestore {
        * @param unit - The unit of time for the difference (e.g., "day", "hour").
        * @returns A new `Expression` representing the difference as an integer.
        */
-      timestampDiff(
-        start: string | Expression,
-        unit:
-          | 'microsecond'
-          | 'millisecond'
-          | 'second'
-          | 'minute'
-          | 'hour'
-          | 'day',
-      ): FunctionExpression;
+      timestampDiff(start: string | Expression, unit: TimeUnit): FunctionExpression;
 
       /**
        * @beta
@@ -5750,15 +5723,22 @@ declare namespace FirebaseFirestore {
 
     /**
      * @beta
-     * Time granularity used for timestamp functions.
+     * Time unit used for timestamp functions.
      */
-    export type TimeGranularity =
+    export type TimeUnit =
       | 'microsecond'
       | 'millisecond'
       | 'second'
       | 'minute'
       | 'hour'
       | 'day'
+
+    /**
+     * @beta
+     * Time granularity used for timestamp functions.
+     */
+    export type TimeGranularity =
+      | TimeUnit
       | 'week'
       | 'week(monday)'
       | 'week(tuesday)'
@@ -5767,11 +5747,11 @@ declare namespace FirebaseFirestore {
       | 'week(friday)'
       | 'week(saturday)'
       | 'week(sunday)'
-      | 'isoWeek'
+      | 'isoweek'
       | 'month'
       | 'quarter'
       | 'year'
-      | 'isoYear';
+      | 'isoyear';
 
     /**
      * @beta
@@ -10525,13 +10505,7 @@ declare namespace FirebaseFirestore {
      */
     export function timestampAdd(
       timestamp: Expression,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day',
+      unit: TimeUnit,
       amount: number,
     ): FunctionExpression;
     /**
@@ -10550,13 +10524,7 @@ declare namespace FirebaseFirestore {
      */
     export function timestampAdd(
       fieldName: string,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day',
+      unit: TimeUnit,
       amount: number,
     ): FunctionExpression;
     /**
@@ -10594,13 +10562,7 @@ declare namespace FirebaseFirestore {
      */
     export function timestampSubtract(
       timestamp: Expression,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day',
+      unit: TimeUnit,
       amount: number,
     ): FunctionExpression;
     /**
@@ -10619,13 +10581,7 @@ declare namespace FirebaseFirestore {
      */
     export function timestampSubtract(
       fieldName: string,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day',
+      unit: TimeUnit,
       amount: number,
     ): FunctionExpression;
 
@@ -11453,14 +11409,7 @@ declare namespace FirebaseFirestore {
     export function timestampDiff(
       endFieldName: string,
       startFieldName: string,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day'
-        | Expression,
+      unit: TimeUnit | Expression,
     ): FunctionExpression;
 
     /**
@@ -11481,14 +11430,7 @@ declare namespace FirebaseFirestore {
     export function timestampDiff(
       endFieldName: string,
       startExpression: Expression,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day'
-        | Expression,
+      unit: TimeUnit | Expression,
     ): FunctionExpression;
 
     /**
@@ -11509,14 +11451,7 @@ declare namespace FirebaseFirestore {
     export function timestampDiff(
       endExpression: Expression,
       startFieldName: string,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day'
-        | Expression,
+      unit: TimeUnit | Expression,
     ): FunctionExpression;
 
     /**
@@ -11537,14 +11472,7 @@ declare namespace FirebaseFirestore {
     export function timestampDiff(
       endExpression: Expression,
       startExpression: Expression,
-      unit:
-        | 'microsecond'
-        | 'millisecond'
-        | 'second'
-        | 'minute'
-        | 'hour'
-        | 'day'
-        | Expression,
+      unit: TimeUnit | Expression,
     ): FunctionExpression;
 
     /**