--- title: "Dates and numbers ยท Agent Wranglers" url: https://agentwranglers.se/playbook/app-ui/dates-and-numbers updated: 2026-10-20 licence: "All rights reserved" --- # Dates and numbers By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20. > Show times in the user's own time zone, keep calendar dates as dates, and read numbers the way people type them. Most off-by-one-day bugs start here. **For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers app interface playbook: https://agentwranglers.se/playbook/app-ui/dates-and-numbers`. ## Required - [Show times in the user's time zone](https://agentwranglers.se/playbook/app-ui/dates-and-numbers/user-time-zone): Show every moment in time in the user's chosen time zone, and name the zone wherever people in different zones see the same screen. - [Keep calendar dates as dates](https://agentwranglers.se/playbook/app-ui/dates-and-numbers/calendar-dates): Keep a value with no time of day, such as a due date, as a plain `YYYY-MM-DD` date everywhere. Never turn it into a moment in time. ## Recommended - [Read numbers the way people type them](https://agentwranglers.se/playbook/app-ui/dates-and-numbers/locale-number-input): Read numbers and amounts in the user's locale, so `1 234,50` in Sweden and `1,234.50` in the US both mean the same amount. Never parse money as a floating-point number. ## Optional - [Show relative times with the exact time beside them](https://agentwranglers.se/playbook/app-ui/dates-and-numbers/relative-times): Put each relative time, such as "5 minutes ago", in a `