diff --git a/sqlglot/typing/bigquery.py b/sqlglot/typing/bigquery.py
index 4026d51729..abf77581e6 100644
--- a/sqlglot/typing/bigquery.py
+++ b/sqlglot/typing/bigquery.py
@@ -9,6 +9,36 @@
     from sqlglot.optimizer.annotate_types import TypeAnnotator
 
 
+# DATE_ADD / DATE_SUB / *_TRUNC return the type of their first argument. BigQuery
+# implicitly casts a string literal first arg to the function's own temporal type,
+# so map each to that type (e.g. DATE_ADD('2020-01-01', ...) -> DATE,
+# TIMESTAMP_TRUNC('...') -> TIMESTAMP).
+_DATE_FUNC_LITERAL_TYPE: dict[type[exp.Expr], exp.DType] = {
+    exp.DateAdd: exp.DType.DATE,
+    exp.DateSub: exp.DType.DATE,
+    exp.DateTrunc: exp.DType.DATE,
+    exp.DatetimeTrunc: exp.DType.DATETIME,
+    exp.TimestampTrunc: exp.DType.TIMESTAMPTZ,
+}
+
+
+def _annotate_date_func(self: TypeAnnotator, expression: exp.Expr) -> exp.Expr:
+    """Annotate DATE_ADD / DATE_SUB / *_TRUNC, which return their first arg's type.
+
+    A typed first argument keeps its exact type (e.g. DATE_ADD(DATETIME, ...) ->
+    DATETIME). For a string literal first argument, BigQuery implicitly casts it to
+    the function's own temporal type, so the result is that type (e.g.
+    DATE_ADD('2020-01-01', INTERVAL 1 DAY) -> DATE).
+    """
+    this = expression.this
+
+    # BigQuery rejects expressions like DATE_ADD(c, ...); it requires the first argument to be a literal
+    if isinstance(this, exp.Literal) and this.is_string:
+        return self._set_type(expression, _DATE_FUNC_LITERAL_TYPE[type(expression)])
+
+    return self._annotate_by_args(expression, "this")
+
+
 def _annotate_math_functions(self: TypeAnnotator, expression: exp.Expr) -> exp.Expr:
     """
     Many BigQuery math functions such as CEIL, FLOOR etc follow this return type convention:
@@ -175,9 +205,6 @@ def _annotate_array(self: TypeAnnotator, expression: exp.Array) -> exp.Array:
         for expr_type in {
             exp.ArgMax,
             exp.ArgMin,
-            exp.DateAdd,
-            exp.DateTrunc,
-            exp.DatetimeTrunc,
             exp.GroupConcat,
             exp.IgnoreNulls,
             exp.JSONExtract,
@@ -197,12 +224,15 @@ def _annotate_array(self: TypeAnnotator, expression: exp.Array) -> exp.Array:
             exp.SafeNegate,
             exp.Sign,
             exp.Substring,
-            exp.TimestampTrunc,
             exp.Translate,
             exp.Trim,
             exp.Upper,
         }
     },
+    **{
+        expr_type: {"annotator": lambda self, e: _annotate_date_func(self, e)}
+        for expr_type in _DATE_FUNC_LITERAL_TYPE
+    },
     **{
         expr_type: {"returns": exp.DType.BIGINT}
         for expr_type in {
diff --git a/tests/fixtures/optimizer/annotate_functions.sql b/tests/fixtures/optimizer/annotate_functions.sql
index f8a9b9482d..f54ef2397a 100644
--- a/tests/fixtures/optimizer/annotate_functions.sql
+++ b/tests/fixtures/optimizer/annotate_functions.sql
@@ -2448,6 +2448,74 @@ DATETIME;
 DATE_ADD(DATETIME '2008-12-25 15:30:00', INTERVAL 30 MINUTE);
 DATETIME;
 
+# dialect: bigquery
+DATE_ADD('2008-12-25', INTERVAL 5 DAY);
+DATE;
+
+# dialect: bigquery
+DATE_TRUNC('2008-12-25', MONTH);
+DATE;
+
+# dialect: bigquery
+DATETIME_TRUNC('2008-12-25', DAY);
+DATETIME;
+
+# dialect: bigquery
+DATETIME_TRUNC('2008-12-25 15:30:00', DAY);
+DATETIME;
+
+# dialect: bigquery
+TIMESTAMP_TRUNC('2008-12-25 15:30:00', DAY);
+TIMESTAMP;
+
+# dialect: bigquery
+TIMESTAMP_TRUNC('2008-12-25', DAY);
+TIMESTAMP;
+
+# dialect: bigquery
+DATE_SUB('2008-12-25', INTERVAL 1 MONTH);
+DATE;
+
+# dialect: bigquery
+DATE_SUB(DATE '2008-12-25', INTERVAL 1 MONTH);
+DATE;
+
+# dialect: bigquery
+DATE_SUB(DATETIME '2008-12-25 15:30:00', INTERVAL 1 DAY);
+DATETIME;
+
+# dialect: bigquery
+DATE_SUB(TIMESTAMP '2008-12-25 15:30:00', INTERVAL 1 HOUR);
+TIMESTAMP;
+
+# dialect: bigquery
+DATETIME_ADD('2008-12-25 15:30:00', INTERVAL 1 DAY);
+DATETIME;
+
+# dialect: bigquery
+DATETIME_SUB('2008-12-25 15:30:00', INTERVAL 1 DAY);
+DATETIME;
+
+# dialect: bigquery
+TIMESTAMP_ADD('2008-12-25 15:30:00', INTERVAL 1 HOUR);
+TIMESTAMP;
+
+# dialect: bigquery
+TIMESTAMP_SUB('2008-12-25 15:30:00', INTERVAL 1 HOUR);
+TIMESTAMP;
+
+# dialect: bigquery
+TIME_ADD('08:50:48', INTERVAL 1 HOUR);
+TIME;
+
+# dialect: bigquery
+TIME_SUB('08:50:48', INTERVAL 1 HOUR);
+TIME;
+
+# dialect: bigquery
+TIME_TRUNC('08:50:48', HOUR);
+TIME;
+
 # dialect: bigquery
 UNIX_DATE(tbl.date_col);
 BIGINT;