[cobanfurkanx]

Closes #2216

Summary

• While a backup or export is still in progress (STARTED / TRANSFERRING), Weaviate serializes the unset Go strfmt.DateTime struct as "0001-01-01T00:00:00.000Z", which Pydantic previously parsed into datetime(1, 1, 1, tzinfo=TzInfo(0)) instead of None.
• Add an after field validator on BackupListReturn.completed_at and ExportStatusReturn.completed_at to normalize year-1 zero timestamps to None while preserving valid completion timestamps.
• Add unit test coverage in test/test_backup.py.

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[weaviate-git-bot]

To avoid any confusion in the future about your contribution to Weaviate, we work with a Contributor License Agreement. If you agree, you can simply add a comment to this PR that you agree with the CLA so that we can merge.

beep boop - the Weaviate bot 👋🤖

PS:
Are you already a member of the Weaviate Forum?

[cobanfurkanx]

To avoid any confusion in the future about your contribution to Weaviate, we work with a Contributor License Agreement. If you agree, you can simply add a comment to this PR that you agree with the CLA so that we can merge.beep boop - the Weaviate bot 👋🤖PS:Are you already a member of the Weaviate Forum?

i agree