Multiple entries can be merged into a single entry. As entries only support one date, time, and location, the earliest information is retained when merging entries into one.
On iPhone, tap the More button (•••) at the top right, then Select Entries to initiate the Multi-Select tool. Or swipe from right to left on an entry in the Timeline and then tap the Checkmark icon. Select the desired entries to merge, the tap the Merge icon at the bottom right.
Select multiple entries using Command+click on the Timeline. Then use right-click (or Control+click) and choose Edit > Merge.