pg_dump custom archive and create backup date
You can use pg_restore -l &lt;custom_dump_file&gt; and the output should start with something like the following:

;
; Archive created at 2019-02-13 22:59:59 UTC
;     dbname: &lt;database_name&gt;
;     TOC Entries: 2615
;     Compression: -1
;     Dump Version: 1.13-0
;     Format: CUSTOM
;     Integer: 4 bytes
;     Offset: 8 bytes
;     Dumped from database version: 10.6 (Ubuntu 10.6-1.pgdg16.04+1)
;     Dumped by pg_dump version: 11.1 (Ubuntu 11.1-3.pgdg16.04+1)
;


As you see, the "Archived created at" line is probably what you're looking for.