Important part is that how datetime format is specified in each country based csv file.
Org time zone is GMT and dataloader timezone is GMT and all the datetime of csv files are in this format
- 2017-04-10 00:00:00
Then you are safe to upload the data.
Org time zone is GMT and dataloader timezone is GMT
Let's say, check the country data whose timezone is GMT+1 hour is specified as
Then importing file from dataloader will not be an issue.
Salesforce stores the datetime in GMT format and will be shown to the user based on user's timezone.
If the csv contains the format without any timezone then following data will take GMT timezone:
So, it will be advisable to match csv datetime zone with dataloader timezone.