Custom time on alert mutes

I would really like to see the ability to set custom times when muting alerts. Right now I can mute for 1 hour or 1 day, but nothing in between. Some times I need to mute an alert for 2 hours or until tomorrow morning.

A few more options would be nice, but really I need the ability to pick any time frame. A field where I can just type a number of hours or days would be good. A date/time picker could work as a way to set when the mute should expire as well.