How do I check when my bandwidth will be reset?

You can check your data usage and reset date on the Overview tab of My Account: windscribe.com/myaccount. The Data Usage card shows how much data you have Used and how much you have Left, and the Resets line below them shows the date your data resets:

On an unlimited plan, the card shows Used and Remaining (Unlimited) instead, with no reset date, because your data never runs out.