When using Gnus, how can I display old messages from a certain time period in article buffer?
Look in the Gnus Info page Gnus > Summary Buffer > Limiting
Limiting means you limit the summary buffer to just show some subset of the articles currently in the group. The particular command you are looking for is:
Ask for a number and then limit the summary buffer to articles older than (or equal to) that number of days (‘gnus-summary-limit-to-age’). If given a prefix, limit to articles younger than that number of days.
(as Arash mentioned)