Relative dates for start/end of period in query building

In building queries in powerBI and Excel, I often wanted endofMonth, startofmonth, endofyear and startofyear for a relative date.

i.e. compare this month (start and end of current month) with last month (start and end of current month - 1).

In mQuery there are a load of these functions Date.StartOfMonth etc which can all be used in filtering data in the PowerBI query engine.