In Datastream you can select the variable Accounting Standard Followed “WC07536” (from Worldscope). In your output you will see a number, in the definition you can find the meaning of the numbers. For example 23 = IFRS and 03 = U.S. standards (GAAP). This is a historical datatype, so you can get it also for previous years (allowing you to find out when a change occured).
In CompuStat Global you can mark ACCTSTD — Accounting Standard – here you’ll get a code of two letters in your output. You have to check the definition to see that DI means “Domestic standards generally in accordance with or fully compliant with International Financial Reporting Standards (IFRS).”
Orbis calls this variable ‘Accounting practice’. Here history is also available (up to 10 years). In the output you’ll see IFRS, Local GAAP or Accounting practice unknown.