Set a challenge — 30 days, 3 months and 14 days, or any exact date range — and get a day-by-day board that fills in as time passes. Every day you skip gets a red cross, every day you show up gets a green check, so you always know exactly how many days you have left and how many you've already spent.
A day-challenge tracker only works if it's honest about the calendar, so this one anchors every challenge to a real start date and calculates each day's status from today's actual date rather than a simple counter you click up manually. Every day between the start and end date gets marked automatically as completed, missed, or upcoming based on whether you checked in before it passed, which is what drives the green checks and red crosses on the calendar grid.
Once a day is in the past and wasn't marked complete, it's recorded as missed with a red cross and stays that way — the tracker doesn't retroactively let you complete a day after it's gone, since the point is an honest record of what you actually did. Your streak and completion count reflect that missed day going forward.
No — everything, including every challenge you create and every day you mark, is stored only in this browser's local storage on this device. It won't sync to another browser or device, and clearing your browser's site data will erase it, so back up anything you care about before doing that.
Restarting resets the challenge's start date to today and clears its day-by-day overrides, which effectively begins the count fresh. If you want to preserve the old attempt's record, create a new challenge instead of restarting the existing one, since restarting overwrites that challenge's own history.