Not another calendar app
You don't always need your full calendar. Sometimes you just want to count the days between two dates, figure out which week a deadline falls on, or sketch out a rough timeline for a project. Opening Google Calendar or Outlook for that means signing in, waiting for it to load, and getting distracted by all the meetings you'd rather not think about.
The 1tt.dev Calendar is built for those moments. It opens instantly, has no accounts to connect, and focuses on one thing: letting you look at dates and mark things on them.
What it's good at
Counting days
Drag across any range of days to select them. The sidebar instantly shows you how many days you've selected, how many are weekdays vs weekends, and the exact date range. No mental math, no Googling "days between two dates."
Marking milestones
Select a date range and create a marker — give it a label and a color. Markers span across the calendar cells so you can visualize how long something takes and how different things overlap.
This is useful for rough project timelines: mark your sprints, deadlines, vacations, or release windows. You get a visual sense of the plan without building a full Gantt chart.
Zooming in and out
Five views let you look at time at different scales:
- Day — 24-hour timeline with a live "now" indicator
- Week — 7-day grid with hourly rows
- Month — the classic month grid, showing markers that span across days
- Quarter — 3 months side by side for mid-range planning
- Year — all 12 months at once for the big picture
Switch between them to plan at whatever granularity makes sense. Quarter view is especially useful for roadmap-style planning where you need to see a few months at a glance.
When to use it
Quick date math
"How many working days until the deadline?" "What day of the week is March 15th?" "If I start on Monday and need 10 business days, when does it end?" — select, read the sidebar, done.
Sketching a project timeline
You're in a meeting or planning session and need to map out rough phases. Open the calendar, mark the key dates with colored markers, and you have a visual timeline in seconds. Share your screen — everyone can see it.
Avoiding your real calendar
Sometimes you need a calendar view that's not tied to your email or work account. Planning a personal trip, checking holiday dates, or figuring out a side project schedule — things that don't belong in your work calendar and don't need the overhead of a calendar app.
Sprint and release planning
Mark your sprints, code freezes, and release dates. The summary in the sidebar shows you the total span, how markers overlap, and how many days each phase covers. It's lighter than a project management tool but more visual than a spreadsheet.
State and sync
Markers are saved to localStorage automatically, so they survive page reloads. If you're signed in, you can enable cloud sync to keep your markers across devices. The calendar is always ready when you come back.
There's no import/export, no iCal integration, no event invites. That's the point — it's a calendar you can use without any setup, for the kind of planning that doesn't need a full productivity suite.