Paul Kemp's latest books, well latest to me, has a very good version of time keeping. It is set in the Realms but I am guessing there is historical precedence to it.
Some place, whether a temple because of religion or a government building, rings a bell every hour after sunrise. This isn't precise, as you can tell, because some days will have more than others, except near an equator type place. However, like anything, the inhabitants adapt to the time keeping system. This sets up, "meet at the 6th hour", which means 6th ring after sunrise. Also, "meet at the last bell", "meet around halfway between 9th and 10th bell", etc. Again, not accurate but something they would learn easily.
I like this, personally, but have to admit for my own games that I do handwave it. I am actually trying to show that for adventuring a given hour, while important to a particular person's life, doesn't see much happen. Things take time. Hmmm. What I mean is, if the adventure is in town, each hour, each minute counts. However, if the group has to travel at all, or if they do travel, suddenly the time frame goes to weeks, perhaps months of inactivity as they travel.
(btw, I believe it was in the 16th century that someone made a clock to keep time down to minutes and possibly seconds. It wasn't until the 19th century, with train schedules, that the time zones and a formal country wide system of time was created. Before then, each town/state/area had its own time.)
Good question! Thanks!
Have a good one! Take care!
edg