Date - Time

[astrodon]

I am not usually so thick but, is it just me or did the designers have a bet on whether or not they could make Dates & Times in PHP absolutely the most vague, convaluted piece of crap possible?

And time began AD 1970? Sup with that?!

:rolleyes: :bemused: 😕

Or maybe there is a source that explains it much better than the book I am using...

Anyone know of any? Searches on this site didn't turn up much.

TIA

[mtmosier]

Here's my understanding about 1970. All "facts" subject to correction.

PHP uses unix timestamps to do its date calculations. Unix was created in 1970, and its creators decided to have a timestamp value which would be the number of seconds passed since.... They picked an arbitrary date, the beginning of that year.

So for unix, yes, the beginning of time was in 1970. If you disagree with php's usage of unix timestamps you can take it up with the developers.

If there is more which you consider vague and convaluted, please point it out. Someone may be able to clearify.

As for further reading, the manual is always a good place to start.

[astrodon]

I suppose then the question is how would one calculate time beyond 1970? Even I know -1 is a wrong answer ;-)

I will check out the manual link as suggested.

Thanks
🆒

[mtmosier]

As you'll see in the manual, -1 does actually work for some operating systems. Works for me. At least back until late 1901 anyway.

If you read through the user comments on the date page you can find suggestions on how to handle dates prior to 1970.

[devinemke]

unix timestamps are a standard way of representing temporal data. let's say you have two separate systems that store date/times:

1. 2005-03-18 13:38:03
2. Friday, March 18th at 1:39pm

how do you compare them? which one is earlier/later? these two dates are just strings that cannot be easily compared/added/subtracted.

this is where unix timestamps come in. a unix timestamp is an integer that represents the number of seconds that have elapsed since 1970-01-01 00:00:00 GMT. since they are simple integers, thay are very easily compared and exchanged between different systems. consider this example:

$date1 = '2005-03-18 13:38:03';
$date2 = 'Friday, March 18th 2005 1:39 pm';

$diff = strtotime($date2) - strtotime($date1);
echo $date2 . ' is later than ' . $date1 . ' by ' . $diff . ' seconds';

[astrodon]

Yes, thank you; and as I have since found out.

Problem being what if perchance, I need to deal with times prior to 1970 (and I do)? Shoot I graduated from High School prior to 1970 - so we are talking about really young stuff :rolleyes: 😃

2005 - 1951 = -1 ; :eek:

Thanks again...

[devinemke]

Originally posted by astrodon
Problem being what if perchance, I need to deal with times prior to 1970 (and I do)?

negative integers (if your OS supports them)

[astrodon]

Ah yes! There I go with my head up again. I'm sure it does - I will experiment later.

Thanks!