How to change time and date language to English?

If everything except date is in English, then there is a high chance that the value of LC_TIME is something wrong, use localectl command to change it to your desired locale:

sudo localectl set-locale LC_TIME=en_US.utf8

or en_GB.utf8 for UK.

You can also place LC_TIME=en_US.utf8 at this file /etc/default/locale manually if you wish.

data utility uses variable LC_TIME to know what language of days to use. If you want to know if this is really the issue, try:

echo $LC_TIME

then if you dont want to mess up anything, but still have different language in your script just change it in your script like

LC_TIME=en_US.utf8