aws s3 sync --exact-timestamps {from-s3} {to-local} does not check the time correctly.

[h-r-k-matsumoto]

Describe the bug

When running aws s3 sync --exact-timestamps {from-s3} {to-local}, always copying files even if no changes.

Expected Behavior

Once copied a file by sync command, copy does not happen in next time.

Current Behavior

Always copy is happened.
It is caused by the difference in date precision.
I've confirmed that the following command and result.

aws s3 sync --delete --no-guess-mime-type --exact-timestamps s3://src-dir ./dst --dryrun --debug
....
2023-08-10 06:21:26,988 - MainThread - awscli.customizations.s3.syncstrategy.base - DEBUG - syncing: xxx -> xxx, size: 669 -> 669, modified time: 2023-07-26 04:20:07.326000+00:00 -> 2023-07-26 04:20:07+00:00

Here is the point.

modified time: 2023-07-26 04:20:07.326000+00:00 -> 2023-07-26 04:20:07+00:00

When syncing file by aws s3 sync , part of milli seconds is missing, and the date difference happen every time by the below.
https://github.com/aws/aws-cli/blob/develop/awscli/customizations/s3/syncstrategy/exacttimestamps.py#L40

Reproduction Steps

aws s3 sync --delete --no-guess-mime-type --exact-timestamps s3://src-dir ./dst --dryrun --debug

1. Please specify source directory that has files with timestamp has a millisecornds.

Possible Solution

I'm not familiar with Python,but we think 2 options.

a) allow less than 1 sec.
https://github.com/aws/aws-cli/blob/develop/awscli/customizations/s3/syncstrategy/exacttimestamps.py#L40

b) update timestamp with keeeping precise.
https://github.com/aws/aws-cli/blob/develop/awscli/customizations/s3/utils.py#L382

Additional Information/Context

No response

CLI version used

aws-cli/2.13.3 Python/3.11.4 Darwin/22.5.0 exe/x86_64 prompt/off

Environment details (OS name and version, etc.)

Mac OS 13.4.1

[h-r-k-matsumoto]

I saw the following issues, but seems not same is what cause is.
So I created this issue.

• aws s3 sync downloading unchanged files. #7228
• s3 sync repeatedly downloads files without modification #5730

[h-r-k-matsumoto]

Ah.. sorry, this is a same with #5730 (comment).
let me close this ticket.

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