chore(samples): update timezone usage

[daniel-sanche]

Some samples currently use datetime.datetime.utcnow(), which raises a deprecation warning. Update samples to use datetime.datetime.now instead

Fixes b/457135528

[gemini-code-assist]

Summary of Changes

Hello @daniel-sanche, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request updates the codebase to use datetime.datetime.now(datetime.UTC) instead of the deprecated datetime.datetime.utcnow(). This change ensures that all timestamp generation is timezone-aware and aligns with modern Python best practices, preventing future deprecation warnings and potential issues with timezone handling.

Highlights

• Deprecation Warning Resolution: Updated all instances of datetime.datetime.utcnow() to datetime.datetime.now(datetime.UTC) to address deprecation warnings in Python.
• Timezone-Aware Timestamps: Ensured consistent and timezone-aware handling of UTC timestamps across samples, tests, and utility functions, aligning with modern Python best practices.
• Codebase Modernization: Modernized timestamp generation methods throughout the codebase to improve maintainability and prevent future compatibility issues.

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[gemini-code-assist]

Code Review

This pull request correctly addresses the deprecation of datetime.datetime.utcnow() by replacing it with the timezone-aware datetime.datetime.now(datetime.UTC). The changes are applied consistently across various sample and test files. I've suggested a minor simplification in a few places where a redundant timezone was being set. Overall, this is a good and necessary update.

[gemini-code-assist]

The tzinfo=UTC in the replace() call is redundant because datetime.datetime.now(datetime.UTC) already returns a timezone-aware datetime object. You can simplify this.

Suggested change

	datetime.datetime.now(datetime.UTC)
	.replace(microsecond=0, tzinfo=UTC)
	datetime.datetime.now(datetime.UTC).replace(microsecond=0)

[gemini-code-assist]

The tzinfo=UTC in the replace() call is redundant because datetime.datetime.now(datetime.UTC) already returns a timezone-aware datetime object. You can simplify this.

Suggested change

	datetime.datetime.now(datetime.UTC)
	.replace(microsecond=0, tzinfo=UTC)
	datetime.datetime.now(datetime.UTC).replace(microsecond=0)

[gemini-code-assist]

The tzinfo=UTC in the replace() call is redundant because datetime.datetime.now(datetime.UTC) already returns a timezone-aware datetime object. You can simplify this.

Suggested change

	datetime.datetime.now(datetime.UTC)
	.replace(microsecond=0, tzinfo=UTC)
	datetime.datetime.now(datetime.UTC).replace(microsecond=0)