Trying to subset a BigQuery table by a timestamp variable might result in an error similar to the following:

ERROR: Prepare error: googleapi: Error 400: No matching signature for
       operator > for argument types: STRUCT<ts TIMESTAMP>, DATETIME
       Signature: T1 > T1
    Unable to find common supertype for templated
       argument <T1>
      Input types for <T1>:

{STRUCT<ts TIMESTAMP>,        DATETIME}

at [1:54], invalidQuery

There is no workaround for this issue.