bug#37921: date -d "a day ago" differs from date -d "1 day ago"

When I ask date(1) for the date "a day ago", I get a different result from when I ask date(1) for the date "1 day ago". The results differ by 3 hours. If I ask for UTC time, the results differ by 1 hour. I'm not able to find anything in the manual to explain this difference. I realize making sens

bug#37921: date -d "a day ago" differs from date -d "1 day ago"

Thank you, Eric and Berny, for the explanation. I'm glad to see it's intentional. Thanks for teaching me about the military time zones. -Matt