Specifying event times relative to the sun.

Since you can specify where you are, you should also be able to specify events relative to what the sun is doing.
for example:

sandy, remind me to turn on the christmas lights at sunset.

sandy, remind me to meet Mr Earp at the O.K. Corral 30mins before sundown.

sandy, remind me to milk the cows at dawn.

sandy, remind me to fatten the goat three weeks before the vernal equinox.

etc.