Using “the” before ordinal numbers

Question

When learning English I was told that ordinal numbers should always be used with "the" before them. But I often see that this is not always so strict, for example I heard the phrase "April first" instead of "April the first". Or when installing OS Windows we could see "Setup is preparing your computer for first use" phrase on a screen.

When should I use the definite article "the" before "first", "second" and so on?

Answer 1

For dates, there is a difference between British and American English.

"April first" is fine in (spoken) American English, but is uncommon in British English, where is would either be "the first of April" or "April the first".

Incidentally, the different word order here may reflect the fact that Americans tend to write dates with the month first, so for example, 1/31 or Jan 31, compared to British 31/1 or 31 Jan.

Regarding the other example given, it could be argued that the word "its" has been omitted, i.e. "Setup is preparing your computer for its first use"; "the" in this case would imply that it's something else that is being used for the first time, e.g. "Setup is preparing your computer for the first use of the new printer".

Answer 2

If the ordinal numbers are used as adjectives where the ordering is unique and definite, definite article is used. For example: the second time, the third example, the fourth person to call. In other words, once you place an order on objects they hold a unique position in that order.

First use in the "Setup is preparing your computer for first use" phrase does not relate to ordering and hence definite article may be omitted.

However, I think "April the first" is the correct usage. I am drawing a parallel to "the First of April" where the the has to be used.