Time is a terrible measure for tasks - use work units instead.
Why I dislike time units
Time is a terrible unit for estimating how long things will take. If I ask you how long it’ll take to read one chapter of a book you’ll probably give me a number - say, twenty minutes. If I ask you the exact same question on a day you’re stressed, anxious, overworked, or fighting off a cold you’ll give me the same answer. Twenty minutes. Your brain doesn’t instinctively factor in your current state when producing time estimates, it just retrieves a cached average and serves it up like it means something.
This applies to everything. Writing a report, fixing a bug, cleaning the kitchen - you’ll give the same estimate on your best day and your worst day because the unit itself is divorced from the conditions that actually determine how long something takes. Time assumes a constant operator and there is no such thing.
Work units
Instead of asking how long something will take, ask how many units it’ll take. A unit is simple - you sit down, work on the problem, and stop when you genuinely need a break. That’s one unit. Not twenty minutes, not an hour, one unit.
I think you can actually know this intuitively. If someone asks me to read a book I don’t need a timer to tell me that’s three units - one to skim the introduction, one to work through the core chapters, one to review and take notes. Skimming a single chapter? That’s a fraction of a unit. Working through a dense textbook? Five or six, depending on how complex it is. The number comes naturally because you’re estimating the actual shape of the work, not slapping an arbitrary clock measurement on it.
The downside of work units is you can’t really communicate them to other people. “That’ll take three units” means nothing to anyone who isn’t you. But this is a mild problem because communicating in time units is inaccurate at best and dishonest at worst - you’re giving a number you know will be wrong and pretending it’s useful. When communicating deadlines to others you should just give a vague “I hope within a couple of days/weeks” and leave it at that. Nobody actually needs the precision you’re pretending to offer.
The real advantage is that on any given day you know how many units you can handle. Some days you’ve got four or five in you, other days you’re lucky to manage one before your brain taps out. Time estimates can’t tell you this - “I have six hours free” means nothing if you only have the capacity for one unit that day. Work units align the estimate with your actual state, which is the whole thing time fails to do.
Because work units give you more realistic expectations you also don’t get that same sense of failure when things don’t pan out. With time estimates you set a fixed target, miss it, and feel like you underperformed - even if nothing about the task changed, only your capacity did. Work units are inherently dynamic by design. You’re aware from the start that the number of units you can push through today might be different from yesterday, and that’s baked into the system. There’s no failure state because the unit itself shifts with you.