dvb/si/datetime: Add more helper functions.
dvb/si/datetime: Add more helper functions.

svogl/bitstream,kierank/bitstream,theambient/bitstream_c,hiroshiyui/bitstream,hiroshiyui/bitstream,kgmoore/bitstream,kgmoore/bitstream,hiroshiyui/bitstream,kgmoore/bitstream,svogl/bitstream,avble/bitstream,svogl/bitstream,avble/bitstream,gfto/bitstream,gfto/bitstream,kierank/bitstream,avble/bitstream,theambient/bitstream_c