some YARN container events have timestamp of -1

Some events in the YARN container entities have timestamp of -1. The RM-generated container events have proper timestamps. It appears that it's the NM-generated events that have -1: YARN_CONTAINER_CREATED, YARN_CONTAINER_FINISHED, YARN_NM_CONTAINER_LOCALIZATION_FINISHED, YARN_NM_CONTAINER_LOCALIZATION_STARTED.

In the YARN container page,

{
id: "YARN_CONTAINER_CREATED",
timestamp: -1,
info: { }
},
{
id: "YARN_CONTAINER_FINISHED",
timestamp: -1,
info: {
YARN_CONTAINER_EXIT_STATUS: 0,
YARN_CONTAINER_STATE: "RUNNING",
YARN_CONTAINER_DIAGNOSTICS_INFO: ""
}
},
{
id: "YARN_NM_CONTAINER_LOCALIZATION_FINISHED",
timestamp: -1,
info: { }
},
{
id: "YARN_NM_CONTAINER_LOCALIZATION_STARTED",
timestamp: -1,
info: { }
}

I think the data itself is OK, but the values are not being populated in the REST output?