Pick the target date and time and give the event a name. The countdown starts immediately — copy the summary line to paste into a chat, email or status page.
Yes. It updates once a second while the tab is open, so you can leave it on a second screen during a launch or deadline. Nothing is stored, so reopening the page means re-entering the date.
It is the count of Mondays to Fridays left before the target, which is usually a far more useful deadline number than raw calendar days. It does not subtract public holidays, since those vary by country.
Yes. If the target is in the past the tool switches to counting up and tells you how long ago it was, which works nicely for anniversaries, sobriety dates or 'days since the last incident' boards.