Getting numeric timezone in specified format

You would have to manually split the string which is formated by %z as +hhmm or -hhmm. %z has a fixed format. Look at the description of strftime.

Replaced by the offset from UTC in the ISO 8601:2000 standard format ( +hhmm or -hhmm ), or by no characters if no timezone is determinable.

Build one string with date and time. Build a second string with the offset from UTC with %z, insert the : in the second string. Concatenate first and second string.

It tries to interpret %: and it doesn't match a format specifier, so it prints it out as is. But you probably knew that already =)

In your time_to_string function, I would manually insert the ':' into the buffer before displaying it.

The syntax you tried don't exist.

What I would do is calling the function twice : once with "%Y-%m-%d %H%M%S ", and once with "%z", manually add the : in the second string, and then concatenate the two.

To insert the :, you could do an ugly buffer manipulation :

buf2[5]=buf2[4];buf2[4]=buf2[3];buf2[3]=':';strcat(buf,buf2);

Note that the layout isn't likely to change for this specific data, so it's not so ugly.

0r if you really like overkill, a regexp. But you'll need an external library.