How did NASA refer to dates and times of a mission in the 1970s?

Question

Back in the 1970s, how did NASA describe when an event happened during a mission?

For example, when Mariner 10 did its fly-by of Venus, how did the Mariner team refer to that moment in time? Did they use the ordinary date and time from a particular timezone on Earth? Did they count some number of elapsed seconds since the start of the mission?

(Apollo 11, in 1969, appeared to use elapsed days/hours/minutes/seconds from the start of the mission, at least according to transcripts.)

Answer 1

For manned missions, everything was usually tracked in Mission Elapsed Time in days, hours, minutes, and seconds.

I don't know if longer term unmanned interplanetary missions did the same -- they might "re-base" time as they approach a target and use, for example, expected time of closest approach to Jupiter as a reference time, so "PJ -1:00:00" could refer to one hour before closest approach.