Weddingbee boards

i think i read some where online that the wording for invitation should:

1. be all capitalized letters

2. spell out the date and time (ex. "the thirtieth of may, half past one o'clock", rather than 5/30, 1:30pm)

are the above etiquettes true and must do-s? or can it be flexible?

Thank you so much!

one more question, should it be:

Sunday, the Twelfth of September

Two Thousand Ten

at Four o’clock in the afternoon

or

Sunday, the twelfth of September

Two thousand ten

at four o’clock in the afternoon

(please note the difference in bolded capitalized letters)