code: private static boolean sameTenantDefs(TenantDefinition tenantDef1, TenantDefinition tenantDef2) {
          return isEqual(tenantDef1.getProperty(TenantService.CREATED_ON_PROP),
                         tenantDef2.getProperty(TenantService.CREATED_ON_PROP)) &&
                 isEqual(tenantDef1.getProperty(TenantService.CREATED_ON_PROP),
                         tenantDef2.getProperty(TenantService.CREATED_ON_PROP));
      }
docs: stamps, allowing for either property to be null for older definitions.