An amount of time, expressed as counts of standard time units U = {years, months, etc.}.
For example, a week (i.e., weeks -> 1) or three months (i.e., months -> 3). Note that periods
are independent of the timeline. For example, given only the period expression 10 weeks, it
is impossible to assign time points of the form NNNN-NN-NN NN:NN:NN to its start and end.
An amount of time, expressed as counts of standard time units U = {years, months, etc.}. For example, a week (i.e., weeks -> 1) or three months (i.e., months -> 3). Note that periods are independent of the timeline. For example, given only the period expression 10 weeks, it is impossible to assign time points of the form NNNN-NN-NN NN:NN:NN to its start and end.