How to Remember When You Last Did Something: The Simple App Solution

When did you last change your toothbrush? Replace the water filter? Get your eyes tested? Call your grandmother?

If you are like most people, you have no idea. These are not daily habits — they are periodic tasks with no natural reminder system. You do them, life moves on, and three months later you are standing in the bathroom thinking "has it been two months or six?"

This is not a memory problem. It is a tracking problem. And it has a surprisingly simple solution.

The Invisible Tasks Problem

Your brain is excellent at remembering things that happen on a fixed schedule. Monday meetings, daily medication, weekly bin collection — these have external triggers that keep them in your awareness.

But irregular tasks have no trigger. They happen when you remember, and you remember when something goes wrong:

• You notice the water tastes odd → the filter is months overdue
• Your dentist asks when your last visit was → you genuinely cannot remember
• A friend mentions they have not heard from you in ages → guilt

These tasks are not urgent enough to put in a calendar. They are not frequent enough to become habitual. They exist in a blind spot between "too important to ignore" and "too infrequent to remember."

Why Calendars and To-Do Lists Fail

The obvious solution is "just put it in your calendar." But periodic tasks do not work well in calendars for three reasons:

1. You do not know the exact future date. When you change your water filter, you would need to calculate the next change date and create a calendar event. Most people do not do this.
2. Calendars are for appointments. Mixing "dentist on Thursday" with "change toothbrush sometime in the next few weeks" clutters the calendar with different types of information.
3. To-do lists lack time context. A to-do item says "change water filter" but does not tell you how long it has been. Is it overdue or just on your list?

What you actually need is the answer to one simple question: how long has it been since I last did this?

The "When Did I Last" Approach

A days-since tracker flips the model. Instead of planning when to do something next, you simply log when you do it. The tracker then shows you how long it has been.

This is powerful because:

• Logging takes two seconds. Tap the item when you do it. Done.
• The passage of time does the reminding. When the number gets high enough, you know it is time.
• You build a history automatically. Over time, you can see your natural rhythm for each task.

Things Worth Tracking This Way

Here are tasks that are perfect for a "when did I last" tracker:

Home Maintenance

• Air filter replacement (every 1-3 months)
• Gutter cleaning (every 6 months)
• Smoke alarm battery check (every 6 months)
• Deep clean of fridge/oven (monthly)
• Water filter replacement (every 2-3 months)

Health

• Eye test (every 1-2 years)
• Dentist visit (every 6 months)
• Blood test or health check (yearly)
• Replacing toothbrush (every 3 months)
• Skin check (yearly)

Social

• Called parents or grandparents
• Caught up with a specific friend
• Date night with partner
• Visited family
• Sent a thank-you note

Car and Possessions

• Oil change (every 6 months or 5,000 miles)
• Tyre pressure check (monthly)
• Car wash
• Mattress rotation (every 3-6 months)
• Backup phone/computer (monthly)

Pet Care

• Flea treatment (monthly)
• Worming tablet (every 3 months)
• Vet check-up (yearly)
• Grooming appointment
• Nail trimming

How Lapsed Makes This Effortless

Lapsed is built exactly for this use case. Every item you add shows as a floating dot, balloon, or hot air balloon on a visual canvas. Items that are recent stay close to today. Items you have not done in a while drift further away.

Set a threshold and you can instantly see what needs attention — items past their threshold are visually distinct. No need to read numbers or do calculations. Just glance at the canvas and you know.

The best part: you do not need to form a habit. You are not trying to do these things daily. You just log them when they happen, and the app handles the rest.

Read about 10 things worth tracking with a days since counter or learn how a visual tracker makes time tangible.