When crossing an ocean East to West or West to East, you will be crossing many time zones.
Time zones are an artificial creation by humans to help organize our days in a predictable fashion. It is much easier to proclaim that the work day starts at 9am and ends at 5pm and not have to specify where this time is taken and how to convert to your local time.
Time zones change 1 hour every 15 degrees of longitude. This means as you sail across an ocean, every 15 degrees will mean that your clocks will change by an hour.
You have a few choices here on the matter, you could keep your clocks on the same time as the country you departed from or the country you will arrive at, and simply deal with the variance in sunrise and sunset times. You could also adjust your clocks as you progress across the ocean. And lastly, you could ignore the constructs of time zones all together and live by UTC time.
We are buddy boating across the Atlantic with an Australian couple on "Adventurous" and they are advancing their clocks by 1 hour as they cross the time zones.
Maddie has not adjusted the time zone on her phone as we have sailed across two time zones, so it has its own time. I have set my phone to UTC time and simply ignore the constructs of time zones all together.
For me, noon is when the sun is directly overhead. That is when I take the moon sight with the sextant. Time zones make it difficult to know which hour I should be getting ready to take the sight. As we advance East, I know it will be a few minutes earlier than last time. At this current moment, I start getting my sextant ready at 3pm UTC. I am ready and I don't miss the sun.
Now, timezones make it easy for daily living if you live by a clock. You eat breakfast at this time, you eat dinner at that time, you awake at this time, you sleep at that time. But while cruising, all of that can go over the side of the deck! We sleep when we are tired and we eat when we are hungry. Some days, we have one meal, other days are spent cooking and eating in entirety! Since time is immaterial to us, I feel fine having a clock that simply tells me my latitude instead of how to live my life.
With watches Maddie and I don't really follow a time schedule. Instead she does first watch until she is tired. I do the next watch until I am tired. This way, neither of us is forced to be out there if we are falling asleep.
When crossing an ocean, time is a construct that you can use or be used by. On the boat, the choice is yours since no one is telling you what to do.