handles metadata timezone differences in sas

[SInginc]

Dear maintainers and reviewers,

• Previously, it is known that dataset creation/modification time is stored in the header of a SAS dataset. It is assumed that these 2 datetimes are saved as UTC timezone.
• After an investigation, it turns out that SAS will store local time instead of UTC time in the header under some circumstances.

To address this:

1. Found the place where SAS store the timezone difference
2. Convert local time back to UTC time

This PR will:

1. Reads timezone difference (which is stored just after the creation/modification time place)
2. Convert local time to UTC time:
   • Timezone difference is store as seconds between UTC and local time with sign. E.g., Eastern Standard time (UTC-5) is -18000.
   • So, local time minus timezone difference is UTC time (local_time = UTC + diff).

[evanmiller]

If you remove the commented-out code, this should be good to merge. Thanks!

[SInginc]

If you remove the commented-out code, this should be good to merge. Thanks!

Hi @evanmiller , the commented-out code has been removed.

Thank you!