native clock();
native difftime(Time: tTime1, Time: tTime2);
native mktime(tm <tmPtr>);

stock Time: time()
    return Time: gettime();

native asctime(tm <tmPtr>, szBuf[], const iSize = sizeof(szBuf));
native ctime(Time: tTime, szBuf[], const iSize = sizeof(szBuf));
native gmtime(Time: tTime, tm <tmPtr>);
native localtime(Time: tTime, tm <tmPtr>);
native strftime(szBuf[], const iSize, const szFormat[], tm <tmPtr>);

#define CLOCKS_PER_SEC (1000)

enum e_tm {
    tm_sec,
    tm_min,
    tm_hour,
    tm_mday,
    tm_mon,
    tm_year,
    tm_wday,
    tm_yday,
    tm_isdst
};

new
    tm <YourVarName>
;
localtime(time(), YourVarName); // Fill "YourVarName" structure with current date and time data

// Edit some things if you wish
YourVarName[tm_mon] = 2 - 1; // Set to february (make sure to sub. 1 since months are starting from 0-11)
YourVarName[tm_mday] = 10; // Set day to 10
// ...

#include <a_samp>
#include <CTime>

public OnFilterScriptInit() {
    printf("clock: %d", clock()); // Prints the time elapsed since samp_server.exe started
    printf("time: %d", _: time()); // Prints the current time in unix-timestamp
    
    // --
    
    new
        Time: tTime1,
        Time: tTime2
    ;
    tTime1 = time(); // Assign the time as unix-timestamp
    Wait(1); // Wait one second
    tTime2 = time(); // Assign the time as unix-timestamp
    printf("You just waited %d second(s)!", difftime(tTime2, tTime1)); // Prints "You just waited 1 second(s)!"
    
    // --
    
    new
        tm <tmTime>
    ;
    // Modify some data
    // For example I want to know which weekday it was at "20 May 2002"
    tmTime[tm_year] = 2002 - 1900; // (2002) Make sure to always sub. 1900 from the date you want to timestamp since the starting data is 1900
    tmTime[tm_mon] = 5 - 1; // (5 - May) Also make sure you sub. 1 in here because the months are starting from 0-11 in this case
    tmTime[tm_mday] = 20; // (20) Obvious
    
    printf("mktime: %d", mktime(tmTime)); // Prints the unix-timestamp
    // "tmTime" has been modified by mktime, now it will be able to tell you the weekday for example:
    
    static const
        szWeekDay[][] = { // Weekday index start from Sunday as index 0
            "Sunday", "Monday", "Tuesday", "Wednesday",
            "Thursday", "Friday", "Saturday"
        }
    ;
    printf("weekday: %s", szWeekDay[tmTime[tm_wday]]); // Prints "weekday: "Tuesday"
    
    // --
    
    new
        szBuf[32]
    ;
    asctime(tmTime, szBuf, sizeof(szBuf)); // Converts "tmTime" to human-readable date and time
    printf("asctime: %s", szBuf); // Possible output: "Sun Oct 30 23:21:51 2011"
    
    // --
    
    ctime(time(), szBuf, sizeof(szBuf)); // Converts the unix-timestamp to human-readable date and time
    printf("ctime: %s", szBuf); // Possible output: "Sun Oct 30 23:21:51 2011"
    
    
    #define MST (-7)
    #define UTC (0)
    #define CCT (8)

    gmtime(time(), tmTime); // Fills "tmTime" structure with the current time expressed as UTC (GMT timezone)
    
    printf("Phoenix, AZ (U.S.) :  %2d:%02d", (tmTime[tm_hour] + MST) % 24, tmTime[tm_min]); // Possible output: "Phoenix, AZ (U.S.) :  15:30"
    printf("Reykjavik (Iceland) : %2d:%02d", (tmTime[tm_hour] + UTC) % 24, tmTime[tm_min]); // Possible output: "Reykjavik (Iceland) : 22:30"
    printf("Beijing (China) :     %2d:%02d", (tmTime[tm_hour] + CCT) % 24, tmTime[tm_min]); // Possible output: "Beijing (China) :      6:30"
    
    // --
    
    localtime(time(), tmTime); // Fills "tmTime" structure with the current time
    strftime(szBuf, sizeof(szBuf), "%A %d %B %Y %H", tmTime); // Format "tmTime" structure as you want
    printf("strftime: %s", szBuf); // Possible output: "strftime: Sunday 30 October 2011 23"
    return 1;
}

stock Wait(iSeconds) {
    iSeconds = clock() + iSeconds * CLOCKS_PER_SEC;
    
    while(clock() < iSeconds) {
    }
}

Wait(5); // Freezes server for 5 seconds

stock GetWeekDay(const iDay, const iMonth, const iYear) {
    new
        tm <tmWeekDay>
    ;
    tmWeekDay[tm_mday] = iDay;
    tmWeekDay[tm_mon] = iMonth - 1;
    tmWeekDay[tm_year] = iYear - 1900;
    
    mktime(tmWeekDay);
    
    static const
        szWeekDay[][10] = {
            { "Sunday" }, { "Monday" }, { "Tuesday" }, { "Wednesday" },
            { "Thursday" }, { "Friday" }, { "Saturday" }
        }
    ;
    return szWeekDay[tmWeekDay[tm_wday]];
}

printf("%s", GetWeekDay(13, 7, 2005)); // Prints "Wednesday"

stock WhichDayWillItBe(const iDay, const iHours)
{
    new
        tm <tmWhichDay>
    ;
    localtime(time(), tmWhichDay);
    
    tmWhichDay[tm_mday] += iDay;
    tmWhichDay[tm_hour] += iHours;
    
    mktime(tmWhichDay);
    
    static const
        szWeekDay[][10] = {
            { "Sunday" }, { "Monday" }, { "Tuesday" }, { "Wednesday" },
            { "Thursday" }, { "Friday" }, { "Saturday" }
        }
    ;
    return szWeekDay[tmWhichDay[tm_wday]];
}

// For example, we are 30 October (Sunday) (2011), 20:00
printf("%s", WhichDayWillItBe(1, 5)); // Prints "Tuesday" (after adding 1 day and 5 hours)

stock Now()
{
    new
        tm <tmToday>
    ;
    localtime(time(), tmToday);

    static
        szStr[64]
    ;
    strftime(szStr, sizeof(szStr), "%A %d %B %Y, %H:%M:%S", tmToday);
    return szStr;
}

printf("%s", Now()); // Possible output: "Monday 31 October 2011, 00:40:30"

new
    tm <tmStamp>
;
localtime(254545645, tmStamp);
    
static
    szStr[64]
;
strftime(szStr, sizeof(szStr), "%A %d %B %Y, %H:%M:%S", tmStamp); // Result: "Wednesday 25 January 1978, 04:07:25"
printf(szStr);

stock Time: cttime()
	return Time: gettime();
//....

new Time: starttime = cttime();
	new
        tm <tmWeekDay>
    ;
    tmWeekDay[tm_sec] = 1 - 1;
    tmWeekDay[tm_min] = 36 - 1;
    tmWeekDay[tm_hour] = 20 - 1;
    tmWeekDay[tm_mday] = 11;
    tmWeekDay[tm_mon] = 04 - 1;
    tmWeekDay[tm_year] = 2012 - 1900;

    new Time:newTime = mktime(tmWeekDay);
    printf("diff: %d seconds", difftime(starttime, newTime));//warning 213: tag mismatch

stock Now()
{
    new
        tm <tmToday>
    ;
    localtime(time(), tmToday);

    static
        szStr[64]
    ;
    strftime(szStr, sizeof(szStr), "%A %d %B %Y, %H:%M:%S", tmToday);
    return szStr;
}