Rescheduling in Google Calendar just got easier. Starting August 13, 2018, Google is introducing a new feature that enables more efficient meeting scheduling. Now, each guest invited to a meeting can propose a new time and the organizer can easily review and accept time proposals. This allows for richer communication between attendees, reduces time spent on meeting practicalities, and makes meetings more productive with key stakeholders in attendance.
When a user is invited to a Calendar event, they can respond “Yes,” “No,” Maybe,” and now, “Propose a new time.” If calendar access permissions have been granted, guests can see the other attendees' availability side by side, so they can suggest a time that works for everyone.
This functionality works across domains and with Microsoft Exchange. Guests can send proposals to organizers using Exchange, and organizers can receive proposals from guests using Exchange.
Source: G Suite Updates Blog: Propose a new meeting time in Google Calendar