Branch merges configured to run daily or weekly do not run

[dibarbet]

@CyrusNajmabadi noticed that none of his feature branches were getting merge PRs created. After looking at the runs in https://devdiv.visualstudio.com/DevDiv/_build?definitionId=12152 it seems like any branch merges configured to run daily or weekly never actually run.

The code to run these merges checks if the run is happening within +/- 5 minutes of 12am midnight.

roslyn-tools/src/GitHubCreateMergePRs/Program.cs

Lines 208 to 235 in 6a3845c

	// Since cron should schedule this to run every 3 hours starting at 12am,
	// we expect to be run within a 10 minute window of this time.
	// Adjust the time 5 minutes into the future in case the pipeline machine
	// and scheduler machine have mismatched clocks.
	var adjustedRunDateTime = runDateTime.AddMinutes(5);
	var adjustedRunDate = adjustedRunDateTime.Date;
	// Because the adjusted run time is being used, we treat a run as valid if
	// it begins within the last 5 minutes of the previous day through the first
	// 5 minutes of the current day.
	var tenMinutes = new TimeSpan(hours: 0, minutes: 10, seconds: 0);
	var isStartOfDay = adjustedRunDateTime - adjustedRunDate < tenMinutes;
	// Daily and Weekly runs only happen at the start of the day
	if (!isStartOfDay)
	{
	return false;
	}
	// Weekly runs only happen on Sunday
	if (frequency == "weekly")
	{
	return adjustedRunDate.DayOfWeek == DayOfWeek.Sunday;
	}
	// Daily runs happen every day
	return true;

I originally thought this might be happening because of a time change - however the pipeline appears to be correctly running at 12am UTC (https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=7229636&view=results), and the code is correctly checking the UTC date. So not sure what is happening. Needs investigation

[RikkiGibson]

Should we change this to make it work based on the age of the most recent auto-PR to the branch?