how do you write time

10:45 am – 12:00 pm Presentation on new business development
The short answer is that although there is nothing wrong with “noon,” I recommend using “12:00 pm,” for the sake of clarity and consistency. The other times listed on your agenda will presumably be written with numbers followed by “am” or “pm” (9:00 am, 10:15 am, 1:30 pm, etc.), and it will be easier to understand if “12:00 pm” is written the same way, especially on an agenda that includes a beginning and an end time for each item, as in this example:

Within a user manual, I need to convey the maximum time period allowed as “365 days 23 hours 59 minutes 59 seconds” – are commas expected between each component? Is the word “and” expected before the last component regardless of the time period name?
I would use commas between each component, and use “and” only if the last component is seconds. I learned way back in intermediate school that “and” is only used before fractions (so 10,247 is said “ten thousand, two hundred forty-seven” but 10 7/8 is said “ten and seven-eighths”). I would call seconds the smallest “lay person” time interval — if you’re getting into fractions of a second, you’ve moved beyond regular timekeeping and are now talking science, so it would be formatted differently.

Well there are a few rules when expressing time. I’ll try to explain in the best way that I can:
Son las tres y media de la tarde.-It is 3:30 in the afternoon.

Es la una (if the time is within the 1 o’clock hour) or Son las + the hour (if the time is after 1 o’clock)
You can also express time numerically.

Seven was a popular approach, but it’s not the only way.
Ehrgott later noted that there seemed to be a camp of Americans who insisted 5 and 8 were the only ways, while across the pond, English writers favored 5 and 6. People had strong feelings about which number they were, including the original tweeter herself.

References:

http://writing.stackexchange.com/questions/6506/how-to-write-time-duration-correctly
http://www.spanishdict.com/answers/124350/how-do-you-write-time-in-spanish-for-example-330p.m
http://www.dummies.com/languages/spanish/telling-time-in-spanish/
http://time.com/5509389/how-do-you-write-the-letter-x/
http://www.computerhope.com/jargon/w/write.htm