how to permanently enable night shift in Mac OSX Sierra?

I'm using Mac OS Sierra on an 11 inch Macbook Air, using an external Acer 24 inch monitor. I would like Night Shift to be always on.

In system preferences -> displays -> Acer G236HL -> the Night Shift tab, here's a picture of the settings:

The closest way to getting what I want is to check "Turn on until tomorrow", which works as expected. However, I have to do this every morning.

I thought I could get an essentially permanent Night shift by using the "schedule" option (with Manual checked off, which I'm reasonably assuming) to set a range beginning 5 min from now, ending 4 min from now, and then waiting 5 minutes. For example, if the time is currently 12:15 PM, I would set the scheduled Night shift to begin at 12:20 PM and end at 12:19 PM, e.g. running for 23 hours and 59 minutes. However, this doesn't seem to work; Night shift simply remains off, and the scheduling option seems to do nothing.

How can I permanently enable Night shift without having to recheck the "Turn on until Tomorrow" box every single morning?

Solution 1:

I just use the schedule with the following custom schedule:

From: 04 AM

To: 03:59 AM

This way it's always on (apart from that minute between).

Note: I don't know if this will work with all external monitors; in which case as suggested you will have to adjust colour profile.