Calendly

Calendly is an app for scheduling appointments, meetings, and events. Its goal is to eliminate the problematic back-and-forth when trying to nail down times. Rather than email chains and phone tag, you can send your availability with a Calendly link (even if the people booking time with you don't use Calendly).

Invitees will see all the available openings in your schedule and can select the one that suits them best. That ensures the ideal time slot for both parties, eliminates time zone confusion, and avoids the strings of conversations about who's available when.