Ignition's DateTime tags, and datetime values/timestamps throughout Ignition, use the java.util.Date data type. This type is fundamentally UTC. Any datetime parsing or printing automatically applies the JVM timezone.
If your MES is supplying UTC timestamps as strings, they will be naïvely interpreted in the gateway's timezone. Then when displayed in a project/client configured to IST, that already wrong timestamp will be butchered further. As you already see.
If you need to parse or stringify timestamps that are not in the Ignition gateway's timezone, you must use java's ZonedDateTime and ZoneId data types instead of Ignition's normal helpers.