Writing the date

[Céline Ancelet]

I need a refresher on how to properly write the date. When should the date be followed by 'th' ? I know there is a rule but I can't remenber it
Is there one more formal or common way to write it?

[Boadicea]

To write the date you have to think of the corresponding ordinal number to the day:

1º - first
2º - second
3º - third
4º - fourth
5º - fifth

Most of the ordinal numbers end in -th, except 1º (st), 2º (nd), 3º (rd) and every other ordinal number ending in 1, 2 or 3 (21º, 42, 93 etc).

Exceptions to this rule are:
11º - eleventh
12º - twelfth
13º - thirteenth

So when you write the date, you write the number + th/st/nd/rd (day) and then the month, for example:

1st September
2nd September
3rd September
4th September
11th September
21st September

I hope it helps. Good luck!