Ask HN: "Time zone" tag feature in communication apps

Recently, I've had to schedule calls with founders and investors from across the world South East Asia to Europe to Latin America. While scheduling, converting time zones is always a task - switch app, check, agree.

Is it difficult to build a feature within communication apps (Email, Chat, DM's etc.) to have a "Time Zone" tag? Similar to a contact tag in email, for example.

The "Time Zone" tag can automatically display the local time of sender or receiver. I know there are tools that can convert time for you and use additional extensions etc. But why not bake it as a feature within such communication apps as scheduling is so important?