You are wondering whether is possible to share an event from another group's calendar on any other group's calendar.
Currently it is not possible, it must be set up a new event within the corresponding SAP Jam group.
2803546 - SAP Jam - Change Time Zone
calendar, group, copy, share, event , KBA , LOD-SF-JAM , SAP Jam , LOD-SF-JAM-GRP , Group Issues , Problem
SAP Jam Collaboration all versions