Is there a way to mark as read all mails before a certain date in Gmail?

Question

When importing a load of messages into Gmail they have all been marked as unread. I don't want to have to go through 15000 emails page by page to mark them as read, is there any way to do this in bulk?

Answer 1

Search for string before:date (date in format yyyy-mm-dd) and then choose More > Select all as read.

Watch out: This will select also emails from this date! I.e. before:2012-07-12 will select email received before 12 July 2012, but also emails received on 12 July 2012.

Answer 2

Search your email with

Before:2012/01/01

And then select them all and mark as read

http://www.mydigitallife.info/how-to-search-messages-within-a-specific-date-range-in-gmail-search-text-box/

Answer 3

You could also use this Google script which automatically marks emails in any Gmail label (inbox also) as read when they become older than N days. Google script to mark old emails as read.

Please note that it is not a one time activity but rather a continuous "check and mark as read" script.