import std;

​

// readable datetime as long to Unix timestamp

// yyyyMMdd

// yyyyMMdd_HHmm

// yyyyMMdd_HHmmss

// TODO ms, us

// see example below

long uts( long v ) {

    import core.stdc.time;

    // a year should be !less than 1970 (unix timestamp)

    // so we can find where yyyy begins

    assert( v >= 1970_01_01, "unsupported format for Unix timestamp" );

    tm t;

    if (v < 1_0000_00_00) { // yyyyMMdd

        t.tm_year = cast( int )(v / 1_00_00 - 1900);

        t.tm_mon = cast( int )(v / 1_00 % 1_00) - 1;

        t.tm_mday = cast( int )(v % 1_00);

        // TODO replace mktime and can be called in compile-time

        return mktime( &t );

    } else if (v < 1_0000_00_00_0000) { // yyyyMMdd_HHmm

        t.tm_year = cast( int )(v / 1_00_00_0000L - 1900);

        t.tm_mon = cast( int )(v / 1_00_0000 % 1_00) - 1;

        t.tm_mday = cast( int )(v / 1_0000 % 1_00);

        t.tm_hour = cast( int )(v / 1_00 % 1_00);

        t.tm_min = cast( int )(v % 1_00);

        return mktime( &t );

    } else if (v < 1_0000_00_00_000000) { // yyyyMMdd_HHmmss

        t.tm_year = cast( int )(v / 1_00_00_000000L - 1900);

        t.tm_mon = cast( int )(v / 1_00_000000 % 1_00) - 1;

        t.tm_mday = cast( int )(v / 1_000000 % 1_00);

        t.tm_hour = cast( int )(v / 1_0000 % 1_00);

        t.tm_min = cast( int )(v / 1_00 % 1_00);

        t.tm_sec = cast( int )(v % 1_00);

        return mktime( &t );

    } else { 

        assert( false, "unsupported format for Unix timestamp" );

        return -1; 

    }

}

​

void main()

{

    2019_07_09_175050.uts.writeln;

    assert( 2019_07_09_175050.uts == 1562694650 ); 

    assert( 20190709_17_50_50.uts == 1562694650 ); 

    2019_07_09_1750.uts.writeln;

    assert( 2019_07_09_1750.uts == 1562694600 );

    2019_07_09.uts.writeln;

    assert( 2019_07_09.uts == 1562630400 );

}