hygiene, provide and use singletons (now_tv() and now_tm()) to obtain the current date/time, ...
hygiene, provide and use singletons (now_tv() and now_tm()) to obtain the current date/time, ...

This changeset should give more robustness because--even though wrong--there
will be just one unique `now' all throughout a run.

Calls like ddiff now now should always return 0, even for nanosecond resolution.

Signed-off-by: Sebastian Freundt <1f0829204b3475c52f714f96be4e7b39a87b6e74@ga-group.nl>

rudimeier/dateutils,rudimeier/dateutils,rudimeier/dateutils