Days Between Dates Mistakes Australians Make and How to Avoid Them

Updated 17 September 2026 · Everyday

A Days Between Dates Calculator gives a fast answer, but the answer is only as good as what goes in. These are the mistakes we see most often with days between dates calculations in Australia, and how to avoid them.

1. Forgetting public holidays

Day counts don’t know about state public holidays, so allow for them in deadlines.

2. Using the wrong units

Australia uses litres per 100 km for fuel and cents per kWh for electricity. Converting from other units introduces errors.

3. Stacking percentages

Percentage changes compound, so they can’t simply be added or subtracted.

4. Ignoring supply charges

Electricity bills include a daily supply charge on top of usage.

5. Overlooking the detail that matters most here

Public holidays differ by state and are not removed from the weekday count.

A quick sense check

Days = end date − start date. Weekdays count Monday to Friday, excluding the end date. With typical inputs the calculator returns days between of 358. If your own result looks wildly different, check that each figure is in the right unit and period (weekly, monthly or yearly) before drawing conclusions.