What is the Correct Form when writing the time – A.M. or a.m. or am?
British style as laid down in the Oxford Guide to Style is 7.30 a.m. There is a note that in Scandinavia, North America and elsewhere the full point between the numerals is replaced by a colon (as on digital watches and clocks). The greatest simplicity is achieved by use of the 24-hour clock: 07.30.