+
+-- |No need to explain.
+showRFC822TimeZone ∷ TimeZone → AsciiBuilder
+showRFC822TimeZone tz
+ | timeZoneMinutes tz ≡ 0 = A.toAsciiBuilder "GMT"
+ | otherwise = show4digitsTZ tz
+
+-- |Convert a 'ZonedTime' to RFC 822 date and time string.
+toAsciiBuilder ∷ ZonedTime → AsciiBuilder
+toAsciiBuilder zonedTime
+ = let localTime = zonedTimeToLocalTime zonedTime
+ timeZone = zonedTimeZone zonedTime
+ (year, month, day) = toGregorian (localDay localTime)
+ (_, _, week) = toWeekDate (localDay localTime)
+ timeOfDay = localTimeOfDay localTime
+ in
+ shortWeekDayName week
+ ⊕ A.toAsciiBuilder ", "
+ ⊕ show2 day
+ ⊕ A.toAsciiBuilder " "
+ ⊕ shortMonthName month
+ ⊕ A.toAsciiBuilder " "
+ ⊕ show2 (year `mod` 100)
+ ⊕ A.toAsciiBuilder " "
+ ⊕ show2 (todHour timeOfDay)
+ ⊕ A.toAsciiBuilder ":"
+ ⊕ show2 (todMin timeOfDay)
+ ⊕ A.toAsciiBuilder ":"
+ ⊕ show2 (floor (todSec timeOfDay) ∷ Int)
+ ⊕ A.toAsciiBuilder " "
+ ⊕ showRFC822TimeZone timeZone