Datasheet

There's pretty much only one way to get the time using the RTClib, which is to call now(), a

function that returns a DateTime object that describes the year, month, day, hour, minute

and second when you called now().

There are some RTC libraries that instead have you call something like RTC.year() and

RTC.hour() to get the current year and hour. However, there's one problem where if you

happen to ask for the minute right at 3:14:59 just before the next minute rolls over, and

then the second right after the minute rolls over (so at 3:15:00) you'll see the time as

3:14:00 which is a minute off. If you did it the other way around you could get 3:15:59 -

so one minute off in the other direction.

Because this is not an especially unlikely occurance - particularly if you're querying the time

pretty often - we take a 'snapshot' of the time from the RTC all at once and then we can pull

it apart into day() or second() as seen above. Its a tiny bit more effort but we think its

worth it to avoid mistakes!

We can also get a 'timestamp' out of the DateTime object by calling unixtime which counts

the number of seconds (not counting leapseconds) since midnight, January 1st 1970

Since there are 60*60*24 = 86400 seconds in a day, we can easily count days since then as

well. This might be useful when you want to keep track of how much time has passed since

the last query, making some math a lot easier (like checking if its been 5 minutes later, just

see if unixtime() has increased by 300, you dont have to worry about hour changes)