PHP daylight saving always false

Question

I would like to know whether a date is in daylight saving time.

So I do this:

echo date('I', strtotime('2017-03-23')); // outputs 0
echo date('I', strtotime('2017-03-29')); // outputs 0

I expect to have different results for the two inputs, as the switch in the UK is 26 March 2017, however the output is 0 in both cases.

I have checked and the time zone looks correct:

echo date_default_timezone_get(); // outputs UTC

Check with `date_default_timezone_set("Europe/London")`, [it works on 3v4l.org](https://3v4l.org/JL2lL) — Pieter van den Ham, Mar 23 '17 at 12:56
I'm guessing being the timezone is UTC you don't have daylight savings time. — John Conde, Mar 23 '17 at 12:57
Related: http://stackoverflow.com/questions/5495803/does-utc-observe-daylight-saving-time — Jeff Lambert, Mar 23 '17 at 12:58

score 3 · Accepted Answer · edited May 23 '17 at 11:54

As you can see in this answer, UTC does not have daylight saving, you need to set your timezone to Europe/London :

date_default_timezone_set('Europe/London'); 
echo date('I', strtotime('2017-03-23')); // echoes 0
echo date('I', strtotime('2017-03-29')); // echoes 1

date_default_timezone_set('UTC'); 
echo date('I', strtotime('2017-03-23')); // echoes 0
echo date('I', strtotime('2017-03-29')); // echoes 0

PHP daylight saving always false

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