END_TIME = 120; //When mission should end in seconds.

if (isServer) then {
[] spawn
{
               ELAPSED_TIME  = 0;
    START_TIME = diag_tickTime;
    while {ELAPSED_TIME < END_TIME} do
    {
        ELAPSED_TIME = diag_tickTime - START_TIME;
        publicVariable "ELAPSED_TIME";
        sleep 1;
    };
};
};

if!(isDedicated) then
{
[] spawn
{
    while{ELAPSED_TIME < END_TIME } do
    {
        _time = END_TIME - ELAPSED_TIME;
        _finish_time_minutes = floor(_time / 60);
        _finish_time_seconds = floor(_time) - (60 * _finish_time_minutes);
        if(_finish_time_seconds < 10) then
        {
            _finish_time_seconds = format ["0%1", _finish_time_seconds];
        };
        if(_finish_time_minutes < 10) then
        {
            _finish_time_minutes = format ["0%1", _finish_time_minutes];
        };
        _formatted_time = format ["%1:%2", _finish_time_minutes, _finish_time_seconds];

        hintSilent format ["Time left:\n%1", _formatted_time];
        sleep 1;
    };
};
};

if (END_TIME <0) then {[b]"end1" call BIS_fnc_endMission;[/b]};

if (END_TIME=0) then {"end1" call BIS_fnc_endMission;};