How can I refer to a period of day when people are awake/active?

Solution 1:

I would say that waking hours, or rather my waking hours is perhaps the most appropriate. This indicates the time spent awake.

If you instead wish to stress that you are not losing time which could be spent working, as opposed to, say, time in the evening, when you would not normally be constructive, I would suggest productive time.

Office or business hours can be used to denote the time of day when working is usually done during the working day.

Solution 2:

In the 1972 movie, "The Cowboys," Wil Andersen (played by John Wayne) says to the young cowboys,

We're burnin' daylight!

(Source: http://www.imdb.com/title/tt0068421/quotes .)

That it is dark when he wakes the young men is not lost on the audience.

So one suggestion (even though the sun may not be up) would be

So I don't have to lose any daylight.

If this is a marketing brochure, you might try

So I don't have to lose any of my busy day.

If you would are searching for something of a higher register, the second definition of diurnal is "Occurring or active during the daytime rather than at night." A parallel (although admittedly more obscure) word is cathemeral, which is described as follows.

A cathemeral organism is one that has sporadic and random intervals of activity during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are performed.

However, it may sound stilted to say that "train travel would lose less of my diurnal period" or "air travel suits my cathemeral nature just fine."

Solution 3:

Daylight hours?

Work day?

Quality time?

Personal prime time?

Solution 4:

Workday (in its “That part of a day in which work is done” sense) may serve. Eg,

Altogether I probably lose four to five hours of the workday when flying. Traveling by overnight train, I don't lose any of the workday itself.