dates with addition

Hi.

1. this is my data for the post date from the XML feed
<date>
<![CDATA[ 2020-03-23 12:52:16 ]]>
</date>

2. i also have on the site an expiry date and i want to populate this field with the data from #1 above plus 60 days.

in other words, how can i add 60 days to the above date record in #1. bearing in mind that upon import , it gets converted to unix.

i need help on this.