History

You may wonder, what did decimal time actually look like in history? I’ve read thousands of records from the Revolution and can tell you. See here for actual examples.

Times were usually spelled out in (French) full words, rather than with numerals and symbols, indicating hours, minutes, and seconds. 12 midnight was written simply as “ten hours decimal” (dix heures décimales), and times after midnight without the hour, as in “one minute decimal,” “two minutes decimal,” etc., until “one hour decimal.” While minutes and seconds might be used, it was common to round to the nearest tenth-hour, called “décime,” about equal to an old quarter-hour. 1:00 AM “old style” might be written “forty-one minutes New style” or simply as “four décimes.” 

If the time had to be abbreviated, as in astronomical time tables, it might be written such as “0 h. 98 m. 76 s.” Doubtless, today it would be written in France the way time is now, with “h” used to separate hours and minutes, so noon would be “5h00” or just “5h.”