:<whatever> means "read it from the <whatever>" file. See the last part of the relevant glibc documentation: https://www.gnu.org/savannah-checkouts/gnu/libc/man

:<whatever> means "read it from the <whatever>" file. See the last part of the relevant glibc documentation: https://www.gnu.org/savannah-checkouts/gnu/libc/manual/html_node/TZ-Variable.html https://www.gnu.org/savannah-checkouts/gnu/libc/manual/html_... However the reason it works without : is that the implementation is being lazy and just ignores the : delimiter and falls back to parsing out a filename either way: https://sourceware.org/git/?p=glibc.git;a=blob;f=time/tzset.c;hb=refs/heads/master#l418 https://sourceware.org/git/?p=glibc.git;a=blob;f=time/tzset....