Hi Sunitha Varadaraju,
You may check the time zone on your portal and SharePoint Online site to see if it is the same as the time zone on your PC. To check it:
In the Office 365 portal:
Log into
Office 365 portal>Click the gear on the upper right corner>Language and time zone.

In the SharePoint Online site:
In the site where you edit a document, click the gear on the upper right corner>Site settings>Under
Site Administration, click Regional settings.>Check the Time Zone.

In your PC:
Search for PC settings or settings>Go to Time and Language to check the time zone.
If that doesn’t help, please confirm the following information to help clarify the situation:
1.Check if the issue happens to newly created files.
2.Confirm whether you are editing a file from your SharePoint Online site or OneDrive for Business library.
3.Open the browser in private mode to check the outcome and change to another browser to see if the issue happens to the specific browser.
4.Open file from another SharePoint Online site to see the outcome.
Thanks,
Felix