How Chronos's scheduling engine fits your tasks into your working hours, and how it adjusts when things change. It follows the rules and settings you choose, so where a task lands is predictable and you stay in control.
By Mark Norton, Founder of Byte Size Labs · Updated 21 October 2026
You add a task with a planned duration, a priority and (optionally) a due date. Chronos finds time for it in your calendar. Here's what happens behind the scenes:
Chronos only schedules tasks inside the weekly hours you set in Settings › Schedule, in your account's timezone. It plans from now to four weeks ahead. If you haven't set any hours, ordinary tasks stay unscheduled. See Setting Your Availability.
Each task gets a score from its priority (Low, Medium, High or Urgent) plus its urgency. Urgency rises as the due date gets closer, and also when there's a lot of work left compared with the time before it's due. Overdue tasks get the biggest urgency boost. When two tasks score the same, the one in an earlier project stage goes first.
Chronos fills free gaps in your hours with work blocks. A block uses as much of a gap as the task needs, so a 3-hour task with a free 3-hour gap stays in one piece. If it doesn't fit in one gap, it's spread across several, even across days. No block is shorter than your minimum work block size, apart from the last bit of a task when less than that is left.
Keeps a gap between scheduled items, including events (10 minutes unless you change it). No buffer is added at the start or end of your working hours.
Time before the due date always comes first. Among the options, Chronos prefers sooner slots, avoids leaving gaps shorter than 15 minutes, and packs work against the edges of your free time so larger stretches stay open. As a deadline gets tight, the earliest slots count for more.
Chronos never fills a day past your Max Scheduled Hours Per Day. Work that can't fit safely is flagged as at risk instead of being crammed in.
Never schedules a task over an event (including events synced from your connected calendars) or over another scheduled task.
Your schedule updates on its own when things change. Tasks and blocks you've pinned by placing them yourself stay where they are. Everything else can move.
Finishing or deleting a task frees up its time.
What happens: Your remaining unpinned tasks are re-planned to use the freed time.
Changing a task's priority, planned duration, due date, earliest start or minimum work block size can change where it belongs.
What happens: Your unpinned tasks are re-planned with the new details.
New hours mean different free time.
What happens: Your unpinned tasks are re-planned inside the new hours.
An event can land on top of a task that's already scheduled.
What happens: Any task that overlaps the event is taken off that time and given a new slot.
A task or block's time passes and it isn't marked complete, and you don't have a timer running on it.
What happens:A few minutes after the slot ends, Chronos moves it to the next suitable time. Pinned items aren't moved.
Buffer time is the break between scheduled items. It gives you room for overruns and a moment to reset.
Max Scheduled Hours Per Day (in Settings › Schedule) is the ceiling Chronos won't fill a day past.
For work that truly can't slip, open the task and turn on Hard due date. A lock icon then shows next to it in your task list.
If the task can't fit before its due date in the normal way, Chronos widens its search, one step at a time:
It never double-books you over an event or another task. If even that isn't enough, the rest is scheduled after the due date and the task is flagged as at risk. A hard-due-date task is scheduled even if you haven't set any working hours.
When Chronos can't schedule a task safely, it tells you. An amber warning triangle appears on the task in the calendar and the task list. Hover over it to see why.
At-risk tasks are marked on your dashboard with these options:
Chronos also notifies you once when a task becomes at risk or can't be scheduled. Turn these off with Scheduling warnings in Settings › Notifications. On Pro and Teams, at-risk tasks also appear in Signals.
The scheduler always follows these rules:
Events (meetings, appointments) keep their times. Chronos never moves them, and schedules tasks around them
Tasks are scheduled and moved automatically. Anything you place yourself is pinned and stays put. See Manual Scheduling
Completed tasks and blocks are never moved, and nor is a task while you have its timer running
Higher-priority tasks generally get placed first, but tasks that are due soon, overdue or have a lot of work left get an urgency boost
Your default is Minimum work block size in Settings › Schedule › Chunk Settings (1 hour unless you change it, 15 minutes at the least). Override it for one task with Min. work block size (optional) under More options when you edit the task. Gaps smaller than the minimum are skipped
Time before the due date is always tried first. If the task can't fit, it's scheduled afterwards and flagged as at risk
A task with an earliest start date and time is never scheduled before it. If that's more than four weeks away, the task waits until it comes into range
A task that has to wait for another task to finish isn't scheduled until that task is complete. See Task Dependencies
A team task is scheduled into its assignee's hours, alongside their own tasks. A team task with no one assigned isn't scheduled automatically
Tasks you add in the app are scheduled the same way, and the app shows each work block where Chronos placed it. At-risk tasks carry an At risk badge. In Agenda and Tasks you can tap it to see why. You can set your working hours and peak hours in the app's Settings. Buffer time, your daily limit and minimum work block size are changed on the web. See iPhone & Android app.
Set accurate availability
Chronos only uses the hours you mark as available, so make them match when you actually work
Use priorities wisely
Don't mark everything as urgent - save it for truly critical tasks
Provide realistic time estimates
Add 20% to your initial estimate to account for interruptions and complexity
Mark events correctly
Use an event for fixed appointments and a task for flexible work
Choose a block size that suits how you work
Smaller blocks (25-30 minutes) fit into a busy day. Larger ones (1-2 hours) keep deep work together. Raise the minimum on a single task when it needs long, focused sessions
Save hard due dates for real deadlines
They can push work into your evenings or past your daily limit, so use them only where a date truly can't move
Drag any task to the time you want and Chronos will leave it there. Learn more in the Manual Scheduling guide.
Need more help? Contact support or return to help centre