If the time displayed on your messages does not match your system clock, there may be an issue with the time zone listed in your Google Account settings.
To fix this issue please follow these steps:
1. Visit https://www.google.com/accounts/ManageAccount?service=mail.
2. Find the Personal Settings and click Edit next to the 'Email addresses' section.
3. For the Time Zone field, choose the time zone that matches your location.
4. Click Save.
5. Sign out of Gmail and sign back in.
OR go via Gmail: Go to settings, then go to accounts tab. On the bottom of page click google accounts setting in the change accounts settings section. Them from there, carry on from step 2 above.