Two confirmed facts in ArmA:
1 - _time is available only for sqs scripts, not for sqf.
2 - time is still reset to 0 after loading any previously saved game (this is quite stupid and disturbing

).
EDIT:
The safe way to do it in sqf (or sqs) is the following:
_timeini = daytime * 3600;
// 30 seconds to wait for something
_waittime = 30;
while {(daytime * 3600) < (_timeini + _waittime)} do
{
.....
};
_timeini = daytime * 3600
_waittime = 30
#loop
_camera camPrepareTarget blabla;
_camera camPrepareRelPos [0,-7,2];
_camera camPrepareFOV 0.700
_camera camCommitPrepared 0
~0.01
?((daytime * 3600) < (_timeini + _waittime)): goto "loop";
daytime is correct all the time, even after loading a game.