#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)(\d+)(?:[.: ](\d\d))*\s*([aApP][.: ]?[mM][.: ]?|o['’]clock)*\s*(?:A(?:C(?:WS|[DS])?T|DT|E[DS]?T|FT|K[DS]T|LMT|M[S]?T|NAS?T|QTT|RT|ST|W[DS]T|Z(?:OS|[OS])?T|oE|T)|B(?:RS|[NORST])T|C(?:AS|ES|H(?:A[DS]|OS|[OU])|ID?S|LS|hS|[ACDEKLOSVX])?T|D(?:AV|DU)T|E(?:ASS?|ES|GS|[ACDEGS])?T|F(?:JS|KS|[EJKN])T|G(?:A[LM]|IL|[EFMSY])T|H(?:OVS?|[DKS])T|I(?:R(?:KS|[DKS])|[CDOS])T|JST|K(?:OS|RAS?|UY|[GS])T|L(?:H[DS]|IN)T|M(?:A(?:GS|[GRW])T|DT|HT|MT|S[DKT]|UT|VT|YT|T)|N(?:FD|OVS?|Z[DS]|[CDFPRSU])T|O(?:MSS?|RA)T|P(?:ETS?|HO|M[DS]|ON|YS|[DEGHKSWY])?T|QYZT|R(?:OT|E)T|S(?:A[KMS]|RE|YO|[BCGRS])T|T(?:AH|OS|[FJKLMORV])T|U(?:LAS?T|TC|YS?T|ZT)|V(?:LAS?|OS|[EU])T|W(?:A(?:RS|[KS])?T|ES?T|FT|GS?T|I(?:TA|[BT])|ST|T)|Y(?:A(?:KS|[KP])|EKS?)T|[ABCDEFGHIKLMNOPQRSTUVWXYZ])"
Local $sString = "12:34 AM ACDT"
Local $sSubst = "$1"
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm