-regexp. This needs to read fully the original mboxes and can take a
-long time. Other conditions have to be fulfilled before the body is
-read though.
+regexp. Evaluatin such a condition requires to read the original
+mboxes completely, which can be slow. However, header conditions are
+checked first to read the bodies only for mails which fulfill them
+entirely.
+.TP
+\fB8h\fR selects mails received during the last 8 hours.
+.TP
+\fBtoday\fR, \fB24h\fR selects mails received during the last 24 hours.
+.TP
+\fBweek\fR selects mails received during the last 7*24 hours.
+.TP
+\fByesterday\fR selects mails received between 48h and 24h ago.
+.TP
+\fBmonday\fR, \fBtuesday\fR, ..., \fBsunday\fR selects mails received
+the most recent such day