Skywatch, our public observing program, is scheduled for 2-3 weekends each month. Each event is:
On a Friday or Saturday evening;
Starts 60-90 minutes after sunset (so the start time changes throughout the year);
And is scheduled to last for one hour.
And if it's on the calendar, you can expect it to happen, unless:
Weather (usually anything involving clouds, and sometimes low temperatures);
Staffing issues (rare, but it could be a thing).
So always check the calendar before you leave your house!