datetime start derivations
- datetime start from datetime and stop - symbol - description - unit - variable name - \(t\) - datetime (mid point) - \(s\) since 2000-01-01 - datetime {time} - \(t_{s}\) - datetime start - \(s\) since 2000-01-01 - datetime_start {time} - \(\Delta t\) - time duration - \(s\) - datetime_length {time} \[t_{s} = t - \frac{\Delta t}{2}\]