Ordinal numbers (Rangtelwoorden)
I’m sure you’ve spotted it …the list on the left of ordinal numbers (rangtelwoorden) is correct. When writing the date in English,we change 1, 2 and 3 into first (1st) second (2nd) and third (3rd). All the other ordinal numbers add ‘th’. The exception to this rule are numbers 11, 12 & 13: they all take ‘th’ (11th, 12th, 13th). After this, it’s back to the original rule.
21th, 22th & 23th are all incorrect, though you’d be surprised how often I have seen this written. It is a mistake to think that you can always add ‘th’ in English to make an ordinal number (rangtelwoord). That would mean saying ‘twenty-oneth’ instead of twenty-first, ‘twenty-tooth’ instead of twenty-second and ‘twenty-threeth’ instead of ‘twenty-third’!
Here’s the tip: Learn 11th, 12th and 13th by heart. For all other dates, add the last two letters of the ordinal number to write the date correctly.
I hope it helps,