[Resolved] Time manipulation problem

chriswheat

Hello,

I am trying to create a "world Clock"

I am using the following code

$timestamp = strtotime("+2 hours");
echo strftime( "%m/%d/%Y %I:%M:%S %p",$timestamp);

Yet Bombay is 13.5 hours ahead of my local time.
If I trie to us the following code I get a blank screen

$timestamp = strtotime("+13.5 hours");
echo strftime( "%m/%d/%Y %I:%M:%S %p",$timestamp);

How do I do a +13.5?

As always Thanks!
Chris

tsinka

Hi,

try

strtotime("+13 hours 30 minutes");

Thomas

chriswheat

I guess that makes since😉

Many thanks works nicely!

Chris

python_q

strtotime("+13 hours 30 minutes") will work
However, since I'm sure some people do not like using strtotime, you can try this instead:

// $zone is the difference in hours from your local time
$offset = 3600*$zone; 
echo strftime("%m/%d/%Y %I:%M:%S %p", time()+$offset);

chriswheat

What is the downside to using strtotime?
and why zone = 3600 ?

how did you come up with that number?

Many thanks
Chris

python_q

Ok, strtotime() works by parsing the given string, looking for keywords like 'days' and 'hours' and then turning this string into a Unix timestamp. This keeps your code rather clean when you need to turn a string like "+1 month 12 days 9 hours 31 minutes 39 seconds" into a time. However, using strtotime() with just one or two units of time is like buying a car in order to get four tires; it gets the job done, but is more costly. You can do the calculations yourself rather simply and without having to parse a string (which takes a lot of computer power compared to simple arithmetic)
A Unix timestamp (which is what time() returns) is simply the number of seconds since January 1, 1970 at midnight GMT (called the Unix Epoch). The 3600 turns the number of hours into seconds (1 hour = 60 min = 60*60 sec = 3600), which is basically the same thing strtotime() does anyway.
Again, both will work, and the speed increase on a small page is negligible, but it's good practice to avoid parsing strings whenever possible.

chriswheat

Thank you for the info. !