set x to current application's NSDate's dateWithNaturalLanguageString_("31 December 1847 11:59:59 AM")
set y to current application's NSDate's dateWithNaturalLanguageString_("31 December 1846 11:59:59 AM")
-- make a date formatter
set df to current application's NSDateFormatter's alloc()'s init()
tell df to setDateStyle_(current application's NSDateFormatterFullStyle)
tell df to setTimeStyle_(current application's NSDateFormatterFullStyle)
-- set formatter's time zone to London, for the great unwashed
set tz to current application's NSTimeZone's timeZoneWithName_("Europe/London")
tell df to setTimeZone_(tz)
-- get date string
display dialog (df's stringFromDate_(x) as text) & ", " & return & df's stringFromDate_(y) as text
Friday, 31 December 1847 1:59:59 AM GMT,
Thursday, 31 December 1846 1:58:44 AM GMT-00:01:15
depending on your date formatting. Notice that the time zone changes, by your 75 seconds.