sfmc-ampscript-first-last-days-of-the-month.html

%%[

set @today = now()
set @monthOfThisMonth = DatePart(@today, "M")
set @yearOfThisMonth = DatePart(@today, "Y")
set @firstDayOfThisMonth = dateparse(concat(@yearOfThisMonth,"-",@monthOfThisMonth,"-01",))
set @nextMonth = dateadd(@today, 1, "M")
set @monthOfNextMonth = DatePart(@nextMonth, "M")
set @yearOfNextMonth = DatePart(@nextMonth, "Y")
set @firstDayOfNextMonth = dateparse(concat(@yearOfNextMonth,"-",@monthOfNextMonth,"-01",))
set @lastDayOfThisMonth = dateadd(@firstDayOfNextMonth,-1,"D")

]%%
@today: %%=v(@today)=%%
<br>@monthOfThisMonth: %%=v(@monthOfThisMonth)=%%
<br>@yearOfThisMonth: %%=v(@yearOfThisMonth)=%%
<br>@firstDayOfThisMonth: %%=v(@firstDayOfThisMonth)=%%
<br>@nextMonth: %%=v(@nextMonth)=%%
<br>@monthOfNextMonth: %%=v(@monthOfNextMonth)=%%
<br>@yearOfNextMonth: %%=v(@yearOfNextMonth)=%%
<br>@firstDayOfNextMonth: %%=v(@firstDayOfNextMonth)=%%
<br>@lastDayOfThisMonth: %%=v(@lastDayOfThisMonth)=%%