I found an unusual domain status of stackbox.com where it is in Pending Delete status as on 5th August, 2019, whereas the Whois expiry date is 24th February, 2020. We all now that Pending Delete is usually the last 5 days of a domain life-cycle. So how is this possible?
This is the correct answer. These records can flip when owners cancel the domain, or even when they renew them during pendingDelete in redemption if their registrar offers it.
I've seen registrars add a year of registration while they wait for the registrant to renew. If the registrant fails to renew, then the registrar will delete the name. Unless of course they have an auction system built in, then they will try to auction the name before they finally delete it.