ASC 842/GASB 87 only
The original ASC 842 standard requires restating your prior comparative years when the new standard is implemented. For most U.S. entities, this means going back two fiscal years from the effective date. Operating leases, which are capitalized under ASC 842, are recalculated as of this earlier date. This is also called the transition date.
In July 2018, the FASB released amendment ASU 2018-11, which allows making the application date the same as the implementation date.
For U.S. public entities using a calendar year fiscal year who choose to restate prior comparative years, this date should be 1/1/2017. For those choosing not to restate prior comparative years, the date should be 1/1/2019.
GASB 87: Paragraph 93 calls for the change to the new standard to be applied retroactively to prior periods presented “if practicable.” To do this, specify the beginning of the prior periods presented as the application date. If restatement is not done, this date should be the same as the effective date above.