The TZONEU2S function might return erroneous results depending on which release of SAS you are executing. The underlying algorithms are based on Internet Assigned Numbers Authority (IANA) tables. Time zone data on SAS^® Viya^®, SAS^® 9.4M8 (TS1M8) with a hot fix, and SAS^® 9.4M7 (TS1M7) with a hot fix are based on IANA 2023c. However, the time zone data in SAS 9.4M8 is based on IANA 2019c, and is thus incorrect.