Present date as first day of the month

问题

In Google Sheets I'm looking for an array formula to provide the first day of a month for a given date. e.g. If A1 is 1/17/12 20:30 B1 would read 1/1/12 and so on. The formula must keep the date format so that I can sort by date, on column B in this example.

回答1:

I think you could just "compose" a new date using the DATE formula. e.g.

=Date(Year(A1);Month(A1);1)

回答2:

Let me add to contribution from Henrique ...

I can use the following arrayformula in cell B1:

=ArrayFormula(if(A:A,eomonth(A:A,-1)+1,))

where column A holds the dates or timestamps

来源：https://stackoverflow.com/questions/8919637/present-date-as-first-day-of-the-month