All the transactions should be imported into Koinly using UTC timezone.
If the transactions are not in UTC, you may experience issues with:
Unmatched transfers
Missing purchase history errors
If timestamps are not in UTC
If the file you exported from your broker/wallet has timestamps in a different timezone, you do not need to edit the file manually. You can offset the timestamps back to UTC upon importing the file to Koinly.
In order to import a file in a different timezone:
Go to file import window as usual (How to import a CSV or Excel file)
After choosing the file and before clicking import, change the Timezone dropdown
You should choose the timezone the files are in
So if your file contains timestamps in EST, you should choose EST in the dropdown
I don't know the timezone
The datetime data in the file is ambiguous by itself. You can't tell from the file if 2022-03-13 09:18 is in UTC, EST, GMT, or any other.
If you do not know the timezone of the timestamps, you need to contact the support of your exchange/service and confirm this.