General guidelines for all texts

5.3 Ordinal numbers

Use digits for ordinal numbers, followed by “st”, “nd”, “rd”, or “th”:

✔️1st  ||  100th

❌hundredth

is it OK to amend this guideline somewhere along these lines:

5.3 Ordinal numbers

Use digits for ordinal numbers, followed by “st”, “nd”, “rd”, or “th”:

✔️1st  ||  100th

❌hundredth

When claim of 100th (year) anniversary is present, word “centenary” can be used instead of "100th". For other multiples use words like bicentennial, tricentennial etc.

While I agree the words centenary, bicentennial, tricentennial etc. should be allowed, I don't understand why that should be discussed in the section on how to present ordinal numbers.

What is the problem  you are trying to solve with this change?

No, nothing special. Its just a proposal to upgrade the rules.

The way the text is written text must be in the guidelines, to avoid using multiple expression to say the same thing.

• 100th anniversary…
• 100 years…
• Centenary…
• … centennial

and I am just focusing in the 100th anniversary, there are other especial words for 5th, 10th,  50th,  1000th…

Sorry… I see “some” reasons to use only one way to write anniversaries:

• Make it easier to search. For example, if we lock for centenaries, we know must search "100th anniversary", and nothing more.
• Provide consistency and coherence to the catalogo, avoiding pages, series… with different expressions to express the same concept.
• Use well-know words, to make the catalogue easier to use for non-native English speakers.