Importing Accounts - to update a field

Importing Accounts - to update a field

Hello,

I have about 500 accounts that need to be updated. The accounts are already in CRM, and I do not want to change anything other then just one field or make a duplicate. I just need the date of a field to be updated. The field that I want to update is united only the dates are different depending on the account. Do you suggest any way how to massively import this update to the field without having to rewrite all the accounts, or me having to update each field in each account separately?

Thank you in advance

Best regards,

Diana