This is a list of time zone abbreviations. Time zones are often represented by alphabetic abbreviations such as "EST", "WST", and "CST", but these are not part of the international time and date standard ISO 8601 and their use as sole designator for a time zone is discouraged. Such designations can be ambiguous; for example, "CST" can mean China Standard Time (UTC+8), Cuba Standard Time (UTC−5), and (North American) Central Standard Time (UTC−6), and it is also a widely used variant of ACST (Australian Central Standard Time, UTC+9:30). Such designations predate both ISO 8601 and the internet era; in an earlier era, they were sufficiently unambiguous for many practical uses within a national context (for example, in railway timetables and business correspondence), but their ambiguity explai