datetime stop derivations

1. datetime stop from start and length

   symbol	description	unit	variable name
   \(t_{e}\)	datetime stop	\(s\) since 2000-01-01	datetime_stop {:}
   \(t_{s}\)	datetime start	\(s\) since 2000-01-01	datetime_start {:}
   \(\Delta t\)	time duration	\(s\)	datetime_length {:}

   The pattern : for the dimensions can represent {time}, or no dimension at all.

   \[t_{e} = t_{s} + \Delta t\]

2. datetime stop from datetime_bounds

   symbol	description	unit	variable name
   \(t^{B}(l)\)	datetime boundaries (\(l \in \{1,2\}\))	\(s\) since 2000-01-01	datetime_bounds {:,2}
   \(t_{e}\)	datetime stop	\(s\) since 2000-01-01	datetime_stop {:}

   The pattern : for the dimensions can represent {time}, or no dimension at all.

   \[t_{e} = t^{B}(2)\]