Date format in Marketing Cloud email based on locale

Question

I am looking to show the date in two different formats based on locale (the locale variable is set to LocaleCode earlier in the email). For en-US it should be January 1, 2021 and all other locales it should be 1 January, 2021. The actual date is being pulled from a data extension and I have it formatted for en-US currently. What I am trying to do is change the format based on the locale. Here is what I have tried (among other things) but it's still not displaying.

TrialEndDate pulls a date from a data extension: SET @TrialEndDate = [ExpirationDate]

%%[
 
    IF @locale == "en-US" then
    SET @date=TreatAsContent(FormatDate(@TrialEndDate, "MMMM d, yyyy"))
    ELSE
    SET @date=TreatAsContent(FormatDate(@TrialEndDate, "d MMMM, yyyy"))
    ENDIF
 
]%%
%%=v(@date)=%%

I had also tried this, without the TreatAsContent function:

%%[

    IF @locale == "en-US" then
    SET @date="%%=FormatDate(@TrialEndDate, "MMMM d, yyyy")=%%"
    ELSE
    SET @date="%%=FormatDate(@TrialEndDate, "d MMMM, yyyy")=%%"
    ENDIF

]%%
%%=v(@date)=%%

Answer 1

You should definitely wrap your send context personalization strings so you can check for empty.

Also, the pattern for the day of the month is dd.

I'd recommend something like this:

%%[

  set @debug = 1
  set @trialEndDate = AttributeValue("ExpirationDate")
  set @locale = AttributeValue("locale")

  if @debug == 1 then
    output(concat("<br>trialEndDate: ", @trialEndDate))
    output(concat("<br>locale: ", @locale))
  endif

  if not empty(@trialEndDate) then

    IF @locale == "en-US" then

       SET @date = FormatDate(@TrialEndDate, "MMMM dd, YYYY")

    ELSE

       SET @date = FormatDate(@TrialEndDate, "dd MMMM, YYYY")

    ENDIF

  else

    set @date = "unknown"

  endif

]%%
%%=v(@date)=%%