When you manually update a schedule item via the editor and publish changes, the information (including any date/time changes) is automatically reflected in the My Schedule section of any user who has added those items to their My Schedule.
When it comes replacing a schedule via CSV import, however, things are a little trickier. This is because its hard for us to know what items are updates versus deletions versus new items.
So here's how it works:
When handling imports that are replacing schedule data, we keep stability for items that are completely identical -- so those items will not be affected in My Schedule.
For any items that are not exact matches, though, we treat them as new, and we delete items not included in the new import. This can have the (possibly unintended) effect of removing items from users' My Schedule lists.