Sql-server – Is MSMerge_History.time in GMT or local server time

Having the date and time separate will allow you to do aggregates by time much easily. for eg: if you want to run a query to find what time period of the day is most busy. This is much easily performed using a separate time dimension.

Also, you should just have one timekey. Decide on either GMT/ EST time - then use this in the fact table. If you need to run reports based off the other timezone, just convert it in your application or query.

When using Merge with identity columns — will need to specify an identity range management option of either automatic or manual so that duplicates do not occur.

With automatic, replication will automatically manage the assignment of identity ranges for nodes participating in the Merge topology.

With manual, you will need to manually assign "islands" of ranges for nodes using DBCC CHECKIDENT.

Have a look at Replicate Identity Columns.