Clicks are now recorded at the moment they happen.
Click times survive a queue backlog. The click worker used to stamp each click with the time it processed it. Whenever the worker paused or the database was briefly unreachable, the backlog drained with fresh timestamps, so clicks bunched up into a few minutes and some landed on the next day. Clicks now keep the time the redirect was served, for v2 clicks, last_click, and v1 daily counters.
last_click never moves backwards. A click that is retried after a newer one no longer overwrites last_click with an older time.