Add count up from specified date and time option

[dziemborowicz]

See also Add an infinite count-up timer option #124.

[lech]

So this enhancement would behave more like a live uptime status by feeding it an accepted standard datetime formatted string or a fuzzy datetime string we can understand. From there Hourglass, could just perform a difference from the local time (unless there's a fancy option to diff on time zones later) and display time remaining until elapsed until it's stopped.

• A simple way would be a "now" option which would start it from the moment you hit "now" and punch in the current datetime
• A datetime in the past would display time elapsed since that date in years, days, hours, minutes, seconds.
• A datetime in the future could display a countdown until that datetime is reached, and once elapsed could continue running a "since…" in years, days, hours, minutes, seconds.