How to enable night light on Ubuntu 16.04

Night light is a feature to make the screen color warmer. It can help to make your eyes feel better when the environment is not very bright.

sudo apt install redshift-gtk

Then run:
redshift-gtk, it will add an icon on the system tray.

cat ~/.config/redshift.conf 
; Global settings for redshift
[redshift]
; Set the day and night screen temperatures
temp-day=5500
temp-night=5300
location-provider=manual
[manual]
; Bay area
lat=37.362578
lon=-122.041881
; Beijing
;lat=39.9042
;lon=116.4074