Whilst blue_cowdawg and kesterkester have already answered this question, I thought I would suggest yet-another-way-to-do-it using a one-liner that could be run directly from the crontab ...

perl -i -pe 's/(\d+)/$1 + 86400/e' timestamp.txt
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perl -le "print+unpack'N',pack'B32','00000000000000000000001010000001'"