Scheduling Tools
Another resource post! This one is for tools that help you schedule meetings/events, particularly with large groups, across time zones, and/or on Discord. This is not a comprehensive list, just tools I've personally tried, but I tried to give some details on the features of each so people can look for one that serves their purpose best. I've included both time finders, which help you find the best time for an event, and time/event displays, which help you announce the event time once you've chosen it (in a way that works across time zones).
Time Finders
Time finding tools help groups find the best time for a synchronous event (like a meeting, watch party, etc.). The user creates a poll with all the possible times, and then anyone interested can fill out the times they are available. Then you'll be able to see who is available at different times. Most online time finder tools have an option to account for time zones. Other potential features include users being able to go back and edit their availability later, comments, different length time slots, etc. Some time finders only let respondents mark themselves as available or unavailable, while others might also include a third option for times in which the respondent could be available if needed, or an "unsure" option.
Below are a list of time finders that I have tried. I've listed details of some features in each, but please note that some of the ease-of-use commentary may be subjective.
Availability response options: Yes/No/If need be. (You can also leave time slots unanswered.)
Comment field: Yes, separate from the response itself (so users can leave multiple comments). Can be disabled.
Accounts: Not necessary, but available.
Results editing: Yes.
Time slot durations: Between 15min and 23h 45 min, in 15 min increments. You can have different duration time slots in the same poll.
Time zone integration: Yes, a toggled option.
Display format: Table, one column for each time slot. (This may involve lots of horizontal scrolling.)
Poll creation ease-of-use: Can be tedious for long periods of time, as you must manually add each time slot (rather than just specifying the entire possible time block), or at least each potential date. There is a button to apply the same set of time options to all dates.
Poll response ease-of-use: The horizontal scrolling can be a bit tedious.
Results viewing ease-of-use: Again with the horizontal scrolling. Each time-slot column displays the number of available respondents on top, and it uses an icon to differentiate between when everyone is available due to all users responding "Yes" vs. at least one "if need be".
Other notes: More features are available with a premium account, but most features are available for free and I have never tried premium (nor have I had any need to).
Sesh is a third-party calendar bot for Discord, which has time finder feature of their own. For full Discord integration, the Sesh bot needs to be added to the server in which the time finder poll is being shared, but the basic time-finder can be used independently of Discord or the Sesh bot. Most features are extremely similar to Rallly, but with the added benefit of Discord integration.
Availability response options: Yes/No/Maybe. (You can also leave time slots unanswered.)
Comment field: None.
Accounts: For creators, none necessary for the basic time finder, can log in with Discord for the full features/integration. For respondents, the creator can choose to make the time finder poll available to anyone with the link (so no account necessary), or they can limit it to members of a specific Discord server.
Results editing: Yes.
Time slot durations: Between 15min and 23h 45 min, in 15 min increments. You can have different duration time slots in the same poll.
Time zone integration: Yes, automatic.
Display format (poll responses): In the browser, it is a table, one column for each time slot. (This may involve lots of horizontal scrolling.) In Discord, it is a vertical list of all the time slots.
Poll creation ease-of-use: (Same as Rallly.)
Poll response ease-of-use: Tedious, both in browser and in Discord. In browser, the horizontal scrolling can be a bit tedious. In Discord, only 4 time slots are displayed at a time and the user must cycle through each set of 4 using forward/back buttons.
Results viewing ease-of-use: Again with the horizontal scrolling, or vertical scrolling if viewing in Discord. A major advantage of this is that Sesh is a calendar bot, so once a time slot is decided upon, a Sesh event (and Discord event, if you've enabled the mirroring setting in Sesh) can be created simply by clicking on that time slot column.
Other notes: Creators can choose to send the time finder poll to Discord, so users can select their availability without even clicking a link. Compared to Rallly, I find the response experience is just a bit clunkier, and viewing the results is not quite as nice a display, but ultimately the difference is very slight. The Discord integration can be a major benefit when event planning, and maybe the event itself, is taking place in Discord.
I haven't used Doodle in quite some time, so I don't have as much up-to-date information on it. I remember it being a nice product on the paid plan my workplace used, but the free version being more limited and annoying.
Availability response options: Yes/no/if need be.
Accounts: Required. Paid plan required for more features.
Results editing: Yes.
Time slot durations: Custom — you can choose any whole number of minutes. You can set different durations in the same poll.
Time zone integration: Yes.
Poll creation ease-of-use: Relatively easy (similar to Rallly and Sesh), but the ads in the free version clog up the interface.
Other notes: Video conferencing integration (Zoom and Google Meet integration available in the free plan, Microsoft Teams and Cisco WebEx only in the pro plan.)
Availability response options: Yes/no.
Comment field: Yes, part of the response.
Accounts: Not necessary, but available.
Results editing: Through a return link shown after the first time submitting, or emailed to the respondent if they choose.
Time slot durations: 15 min, 30 min, 1 hour, 1 day
Time zone integration: Yes, a checkbox option.
Display format: Calendar grid.
Poll creation ease-of-use: Very easy.
Poll response ease-of-use: Easy (the easiest on this list). Built-in zoom slider. Works fine on mobile and touch screens.
Other notes: WhenIsGood has some neat extra features like customizing the event URL, setting default highlighted time slots, etc.
Availability response options: Yes/No
Comment field: None.
Accounts: Not available.
Results editing: Optional password.
Time slot durations: 15 minutes
Time zone integration: Yes for specific dates survey. No for days of the week survey.
Display format: Calendar grid.
Poll creation ease-of-use: Easy.
Poll response ease-of-use: Not particularly intuitive. It is especially difficult to accurately select times on mobile or touch screen devices.
Results viewing ease-of-use: Not great. Alright if you are okay viewing results by color shade. Shows the portion of participants available by the darkness of the color, and then you can hover over a time slot to see who specifically is available.
Time Displays
Event Announcers
Some time zone reference sites have event announcer tools, where you can create a shareable link that shows each viewer a countdown and the event time in their own timezone. Time And Date, 24 Time Zones
Time Zone Converters
You can use converters like these to convert to UTC, if you don't want to do the offset math (or want to avoid any daylight savings related errors).
Time And Date, 24 Time Zones
Discord Specific
Discord Universal Timestamps
Universal timestamps are markdown text that Discord will display in each user's timezone. You can use a converter to generate the text. Converters: EpochConvert, Sesh, Discord Time Stamp
Built-In Discord Server Events
If planning an event in a server that you have "Create Events" permissions in, you can create a server event and the time will automatically show up in each user's time zone.
Sesh is a third-party calendar bot for Discord.
The Friend Time bot can automatically convert between times sent by other users into your own time zone. I am personally not a fan of this option, as it requires every interested party to have set up the bot, and because you reveal your own time zone by necessity when you use it. (There is a private mode which keeps your specific time zone from displaying to other users, but unless you always send times with time zone information attached, e.g. "19:00 UTC", then any other user will be able to know the current time difference between your time zones.) Essentially, it is a way to avoid doing time zone math, but not a way to keep one's own time zone private (and even makes it more public).