--- /dev/null
+[verse]
+__YYYY__-__MM__-__DD__ __HH__:__II__[:__SS__[.__NANO__]]
+__HH__:__II__[:__SS__[.__NANO__]]
+$$[$$-]__SEC__[.__NANO__]
+
+'YYYY'::
+ 4-digit year.
+
+'MM'::
+ 2-digit month (January is `01`).
+
+'DD'::
+ 2-digit day.
+
+'HH'::
+ 2-digit hour (24-hour format).
+
+'II'::
+ 2-digit minute.
+
+'SS'::
+ 2-digit second.
+
+'NANO'::
+ Nanoseconds (up to nine digits).
+
+'SEC'::
+ Seconds since origin.