[Canonical page](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/date-time/>)
[Full documentation index](<https://docs.dhtmlx.com/planning-engine/llms.txt>)


# DateTime

A naive local date-time at minute precision, with no timezone and no DST. Every date the API accepts or returns is a `DateTime`, for example the dates in [`TaskData`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/task-data.md>) and [`SchedulingConfig`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/scheduling-config.md>). Build one with `DateTime::from_ymd_hm` or convert it from a `chrono::NaiveDateTime`.

## Declaration

```rust
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct DateTime(/* private */);

impl Display for DateTime
impl From<chrono::NaiveDateTime> for DateTime
impl From<DateTime> for chrono::NaiveDateTime
```

The inner value is private. `DateTime` doesn't implement `Default` or `FromStr`. With the `serde` feature it also implements `Serialize` and `Deserialize`; see [Serialization](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/date-time.md#serialization>).

Values compare by time: an earlier date-time is less than a later one.

## Associated functions

### from_ymd_hm

```rust
pub fn from_ymd_hm(y: i32, m: u32, d: u32, h: u32, min: u32) -> Option<DateTime>
```

Builds a date-time from calendar fields.

**Parameters**

| Name | Type | Description |
|---|---|---|
| `y` | `i32` | Year. |
| `m` | `u32` | Month, `1..=12`. |
| `d` | `u32` | Day of the month, checked against the month and leap years. |
| `h` | `u32` | Hour, `0..=23`. |
| `min` | `u32` | Minute, `0..=59`. |

**Returns** - `Some(DateTime)`, or `None` when the fields don't form a valid date and time (for example February 30 or hour `24`).

## Methods

### minutes

```rust
pub fn minutes(self) -> i64
```

Minutes since 1970-01-01 00:00, counted as naive time. Dates before 1970 give negative values. The difference of two `minutes()` values is the elapsed wall-clock time between them; no working calendar is applied.

**Returns** - the minute count.

## Conversions

### From&lt;chrono::NaiveDateTime&gt;

```rust
impl From<chrono::NaiveDateTime> for DateTime
```

Truncates seconds and sub-seconds: `2026-03-02 08:15:59` becomes `2026-03-02 08:15`. `plen-core` doesn't re-export `chrono`, so add it to your own dependencies (`cargo add chrono`) to use this conversion.

### From<DateTime> for chrono::NaiveDateTime

```rust
impl From<DateTime> for chrono::NaiveDateTime
```

Returns the same date and time with seconds set to `0`.

## Display

`Display` writes `YYYY-MM-DD HH:MM`, for example `2026-03-02 08:00`.

## Serialization

Requires the `serde` feature:

```bash
cargo add plen-core --features serde
```

- `Serialize` writes the `Display` string, `"YYYY-MM-DD HH:MM"`.
- `Deserialize` reads a string, trims surrounding whitespace and accepts `YYYY-MM-DD HH:MM`, `YYYY-MM-DD HH:MM:SS`, the same two forms with `T` instead of the space, and a bare date `YYYY-MM-DD` (read as `00:00`). Seconds are truncated. Any other string fails with the error message `invalid date`.

## Example

```rust
use plen_core::DateTime;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let start = DateTime::from_ymd_hm(2026, 3, 2, 8, 0).ok_or("invalid date")?;
    let end = DateTime::from_ymd_hm(2026, 3, 4, 17, 0).ok_or("invalid date")?;

    assert!(start < end);
    println!("{start} -> {end}"); // 2026-03-02 08:00 -> 2026-03-04 17:00

    let elapsed_hours = (end.minutes() - start.minutes()) / 60;
    println!("{elapsed_hours} h"); // 57 h

    assert!(DateTime::from_ymd_hm(2026, 2, 30, 8, 0).is_none());
    Ok(())
}
```

## Related

- [`TaskData`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/task-data.md>) - task dates and constraint dates are `DateTime` values
- [`SchedulingConfig`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/data/scheduling-config.md>) - project start and end are `DateTime` values
- [`Mutation`](<https://docs.dhtmlx.com/planning-engine/rust/api/core/results/mutation.md>) - returns computed task dates as `DateTime`
- [Quick start](<https://docs.dhtmlx.com/planning-engine/rust/quick-start.md>) - builds dates with `from_ymd_hm` in a first schedule
- [Project data](<https://docs.dhtmlx.com/planning-engine/rust/scheduling/project-data.md>) - how dates are read in an input snapshot