When to start a virtual challenge: picking your window

Each X Challenge has a fixed window, from 7 days for Loki to 88 days for Dragon. It starts the moment you tap Start in the app. Your registration does not expire before that, so there is no rush to begin the day the confirmation email arrives.

One thing to keep in mind: refunds are available within 30 days of purchase if you have not started. After that, or once you start, the sale is final.

• Trips: a week of travel in a short window is a problem. In a long one it is a gap to make up.
• Work crunches: tax season, year-end, product launches.
• Family events: visitors, school holidays, moves.
• Your health: start when you feel well, not on the last day of a cold.

Then count back. To finish by a set date, start at least the length of the window before it, plus about a quarter more as a buffer.

If you want to be done by a birthday, a trip or a race, work backwards. This table adds about a quarter of the window as a buffer.

Coming back from an illness, an injury or a long stretch of not moving? Start with a challenge that has a low daily average and a long window, and take the first week easier than the plan suggests. Short, frequent walks are a gentler restart than long sessions. If you are recovering from an injury or a medical condition, ask your doctor what is safe before you tap Start.

Some people plan a whole year. The three challenges of Legends Of Asgard add up to 37 days if started one after another, which fits a single season. The Four Holy Beasts adds up to 274 days, about nine months of steady walking. You do not have to run them back to back. A gap of a week or two between challenges is a good rest.

In summer, the CDC advises training earlier or later in the day when it is cooler, starting slowly and drinking before you are thirsty. In winter, layer up, watch for ice and use the treadmill on the worst days. As the days shorten, wear lights and reflective gear.

More in running in the heat, winter running tips and running in the dark.

The weeks from Thanksgiving to New Year are the hardest time to start a short challenge. They suit a long one better, because a few lost days get spread over weeks. Kylin or Dragon started in early December carries a habit through the holidays and well into the new year.

If you are setting a January goal, buy in December and tap Start on a normal weekday, not on the first of the month when everyone else is starting too. See making a New Year fitness goal stick.

The weeks you choose matter, and so does the slot in each day. A fixed time turns a challenge into a routine, and routines survive busy weeks better than good intentions. Morning sessions are less likely to be pushed aside by the rest of the day. Evening sessions suit people who are slow to wake up, and they help you unwind after work. Lunch walks suit office workers and add up surprisingly fast. Try one slot for the first week, then keep it or change it.

A long window will meet bad weather somewhere. Have a plan B before you need it. Treadmill and indoor bike sessions count through the app’s indoor mode, and a mall or a big store is a dry place to walk on a stormy day. Swimming and rowing count too. On days of extreme heat, cold or poor air, the right move is often a rest day, with the distance made up later in the week.

Starting with a friend helps here as well. It is harder to cancel a walk when someone is waiting for you.

1. Check the next week of your calendar and the full window.
2. Know your first three sessions: day, time and route.
3. Charge your phone and check that location access is on for the app.
4. Tell someone. A friend who asks how it is going is worth more than any app reminder.
5. Then tap Start, and do the first session that day if you can.

• Can I buy now and start in a few months? Yes. The window does not start until you tap Start.
• Is it better to start on a Monday? Start on a day you can do a session. Momentum on day one matters more than the day of the week.
• What if I get sick halfway? Rest. Then divide what is left by the days left, and write to support if you need more time.
• Should I start on my birthday or New Year’s Day? A meaningful date helps some people. Just make sure the weeks after it are clear, too.
• Can I start two challenges at once? Check how your challenges appear in the app first. For most people, one at a time is easier to keep up.
• Does daylight saving time matter? It can. When the clocks go back in November, evening walks move into the dark, so plan for lights or a new time slot.

• Heat and Athletes, CDC: train earlier or later in the day when it is cooler, start slowly, and drink before you are thirsty.