Time Converters

Time Conversion: More Than Just Hours and Minutes

You've quoted a client "this will take 120 hours", but you need it in days. Your payroll system wants hours in decimal format (5.5 hours instead of 5:30). You're planning a project and need to know whether something takes 3 weeks or 21 days. Time conversion sounds simple until you realise that months aren't all 30 days and leap years exist.

Start with the conversions everyone knows: 60 seconds = 1 minute, 60 minutes = 1 hour, 24 hours = 1 day, 7 days = 1 week. That's straightforward. The confusion starts with months and years. Is a month 30 days? 28 days? 30.4375 days on average? For financial calculations, Australia uses a 365-day year divided into 12 months of 30.4375 days average. This matters for loan calculations, lease durations, and interest accrual.

Payroll is where decimal hours matter most. If someone works 5 hours and 30 minutes, that's 5.5 hours in decimal. If they work 6 hours and 15 minutes, that's 6.25 hours. Most payroll software requires this format. The formula is simple: minutes divided by 60, added to the hours. 30 minutes = 0.5 hours. 15 minutes = 0.25 hours. 45 minutes = 0.75 hours. Do this wrong and your employee either gets underpaid or you overpay them. MYOB and Xero both have this baked in, but freelancers often use simple spreadsheets where you need to get this right.

Project planning uses mixed units constantly. You might estimate a task as "3 days" but your project manager wants it in hours. A working day in Australia is typically 8 hours, so 3 days is 24 hours. But does that include meetings? Emails? A realistic 3-day task usually requires 30-40 hours of actual work because of context switching and interruptions. Underestimate here and you'll miss your deadline.

Cooking times often mix formats. A recipe says "bake for 45 minutes" but your oven timer only counts down in seconds, so that's 2,700 seconds. Conversely, some professional kitchens use "sear for 90 seconds" which is harder to judge than "90 seconds", so experience matters. Digital timers have made this less critical, but if you're timing something carefully (reducing a sauce, steeping tea), knowing seconds matters.

Travel time calculations get tricky when you mix speed and distance. If you're driving 380 kilometres at 100 km/h, that's 3.8 hours or 3 hours and 48 minutes. Add rest stops and fuel breaks (Australians should add roughly 15 minutes per 2 hours on long drives), and you're looking at closer to 5.5 hours actual elapsed time. This is why "how long to get to Melbourne?" has a different answer depending whether you're asking about driving time or actual journey time.

The biggest gotcha is leap years. Most years have 365 days. Every 4 years, you get a leap year with 366 days (like 2024). But century years (2000, 2100, 2200) are only leap years if divisible by 400. So 2000 was a leap year, but 2100 won't be. This affects holiday calculations and date math, though unless you're writing software, you probably don't care. Your calendar app handles it.