Function Scheduler failing due to incorrect timestamp format

File "/layers/google.python.pip/pip/lib/python3.12/site-packages/firebase_functions/scheduler_fn.py", line 102, in on_schedule_wrapped
    schedule_time = _dt.datetime.strptime(
                    ^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.runtime/python/lib/python3.12/_strptime.py", line 653, in _strptime_datetime
    tt, fraction, gmtoff_fraction = _strptime(data_string, format)
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.runtime/python/lib/python3.12/_strptime.py", line 432, in _strptime
    raise ValueError("time data %r does not match format %r" %
ValueError: time data '2025-10-17T16:50:00.510855-07:00' does not match format '%Y-%m-%dT%H:%M:%S%z'"

This started happening over the weekend with no changes / alterations to our workers. From the internal logic it appears to be sourced at:

    def on_schedule_decorator(func: _C):

        @_functools.wraps(func)
        def on_schedule_wrapped(request: _Request) -> _Response:
            schedule_time: _dt.datetime
            schedule_time_str = request.headers.get(
                "X-CloudScheduler-ScheduleTime")
            if schedule_time_str is None:
                schedule_time = _dt.datetime.utcnow()
            else:
                schedule_time = _dt.datetime.strptime(
                    schedule_time_str,
                    "%Y-%m-%dT%H:%M:%S%z",
                )

So I'm suspecting that the following request.headers.get("X-CloudScheduler-ScheduleTime") has changed? Upgrading the sdk version is likely to be a major endeavour, what's the simplest solution here?

def on_schedule_wrapped(request: _Request) -> _Response:
    schedule_time_str = request.headers.get("X-CloudScheduler-ScheduleTime")

    if schedule_time_str is None:
        schedule_time = _dt.utcnow()
    else:
        try:
            # Supports the expected RFC 3339 format and ISO 8601 as well
            schedule_time = dateutil_parser.isoparse(schedule_time_str)
        except ValueError as e:
            print(f"Failed to parse RFC 3339 timestamp: {e}")
            schedule_time = _dt.utcnow()

Something like the above might be what we would want, since the incoming datetime still satisfies the documented definition, but the current implementation does not.

Reference:
https://cloud.google.com/scheduler/docs/reference/rpc/google.cloud.scheduler.v1#appenginehttptarget

@BennetVellaExient

Hi @BennetVellaExient! Thanks for raising this. It's been received and we will provide updates when available.

fix-cloudscheduler-scheduletime.patch

Content:

diff --git a/src/firebase_functions/scheduler_fn.py b/src/firebase_functions/scheduler_fn.py
index 1979f67..8fee83d 100644
--- a/src/firebase_functions/scheduler_fn.py
+++ b/src/firebase_functions/scheduler_fn.py
@@ -103,10 +103,16 @@ def on_schedule(**kwargs) -> _typing.Callable[[_C], _Response]:
             if schedule_time_str is None:
                 schedule_time = _dt.datetime.utcnow()
             else:
-                schedule_time = _dt.datetime.strptime(
-                    schedule_time_str,
-                    "%Y-%m-%dT%H:%M:%S%z",
-                )
+                try:
+                    # Robust RFC 3339 parsing
+                    schedule_time = dateutil_parser.isoparse(schedule_time_str)
+                except ValueError as e:
+                    print(f"Failed to parse RFC 3339 timestamp: {e}")
+                    schedule_time = _dt.utcnow()
+                        schedule_time = _dt.datetime.strptime(
+                            schedule_time_str,
+                            "%Y-%m-%dT%H:%M:%S%z",
+                        )
             event = ScheduledEvent(
                 job_name=request.headers.get("X-CloudScheduler-JobName"),
                 schedule_time=schedule_time,

Maybe this is of use.

any updates on this, since this is crucial for functions to work properly again

@KoblerS

@KoblerS #256 was a proposed solution for this and @CorieW confirmed they're reviewing this today.

@KoblerS #256 was a proposed solution for this and @CorieW confirmed they're reviewing this today.

thanks for the quick update! :)

fix: add robust date parsing in schedule_fn (firebase#256)

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Function Scheduler failing due to incorrect timestamp format #255

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Function Scheduler failing due to incorrect timestamp format #255

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BennetVellaExient commented on Oct 20, 2025

CorieW commented on Oct 20, 2025

BennetVellaExient commented on Oct 20, 2025

KoblerS commented on Nov 4, 2025

BennetVellaExient commented on Nov 4, 2025

KoblerS commented on Nov 4, 2025

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