Macro from_ymd 

macro_rules! from_ymd {
    ($y:expr, $m:expr, $d:expr; $h:expr, $min:expr, $s:expr, $attos:expr, on=$scale:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr, $min:expr, $s:expr, on=$scale:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr, $min:expr, on=$scale:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr, on=$scale:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr, $min:expr, $s:expr, $attos:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr, $min:expr, $s:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr, $min:expr) => { ... };
    ($y:expr, $m:expr, $d:expr; $h:expr) => { ... };
    ($y:expr, $m:expr, $d:expr, on=$scale:expr) => { ... };
    ($y:expr, $m:expr, on=$scale:expr) => { ... };
    ($y:expr, on=$scale:expr) => { ... };
    ($y:expr, $m:expr, $d:expr) => { ... };
    ($y:expr, $m:expr) => { ... };
    ($y:expr) => { ... };
}

Builds a Dt from a Gregorian calendar date and optional time.

Sugar for Dt::from_ymd.

Date fields are positional (y, m, d). Time is optional: put a semicolon after the day, then hour (required if ; is present), then optional minute, second, and attoseconds. An optional on= civil scale may follow.

Omitted field	Default
month	1
day	1
time (no ;)	0, 0, 0, 0
minute / second / attos after ; h	0
on	Scale::UTC

The resulting Dt’s target field is set from that civil scale (the on= value, or UTC when omitted), as from_ymd does. There is no target= on this macro — chain .target(…) if needed.

Forms

from_ymd!(y)
from_ymd!(y, m)
from_ymd!(y, m, d)
from_ymd!(y, m, d, on=Scale::TAI)
from_ymd!(y, m, d; h)
from_ymd!(y, m, d; h, min)
from_ymd!(y, m, d; h, min, sec)
from_ymd!(y, m, d; h, min, sec, attos)
from_ymd!(y, m, d; h, min, sec, attos, on=Scale::UTC)

Examples

use deep_time::Scale;
use deep_time::from_ymd;

assert_eq!(
    from_ymd!(1970),
    deep_time::Dt::UNIX_EPOCH,
);
assert_eq!(
    from_ymd!(2026, 6, 16),
    deep_time::Dt::from_ymd(2026, 6, 16, Scale::UTC, 0, 0, 0, 0),
);
assert_eq!(
    from_ymd!(2000, 1, 1; 12, on=Scale::TAI),
    deep_time::Dt::ZERO,
);
assert_eq!(
    from_ymd!(2000, 1, 1; 12, 0, 0, 123_456_789, on=Scale::UTC),
    deep_time::Dt::from_ymd(2000, 1, 1, Scale::UTC, 12, 0, 0, 123_456_789),
);

// different target field after construction
let _ = from_ymd!(2020, 1, 1, on=Scale::UTC).target(Scale::TAI);