Center For Practice Management, Ethics, Productivity, Technology

Calculating Dates: Trust, but Verify

Lawyers often need to count days between dates to determine deadlines. A recent discussion on Twitter revealed several tools, some built right into your computer, which can help with this particularly important task. Since deadline related errors are the subject of disciplinary complaints and malpractice claims it is important to get this right! While you can use free tools to get the job done, subscription rules based calendaring tools are the smart way to ensure you calculate the dates according to the jurisdiction’s court rules.

Windows 10

The calculator built into Windows 10 will do many different calculations. The calculator desktop app has “difference between dates” and “add or subtract days” functions and the add/subtract function shows the weekday in the results. How do you find it? Type “calculator” into the search bar in your Taskbar. Then right click to add it to your Taskbar or Pin to Start. To find the functions open the calculator, click on the hamburger menu (three stacked vertical lines) in the upper left corner and pick “Date Calculation”. Then in the drop down choose “Difference Between Dates” or “Add or Subtract Days”.

Desktop Apps

Microsoft Excel

In Excel you can calculate dates in several ways using different formulas. The article from ExtendOffice provides instructions on how to add or subtract days/weeks/months/years or a combination with or without formulas.

Microsoft Outlook

Let Outlook calculate a date for you. Simply create an event and in the date field type in what you want, like “30 days from tomorrow” or “25 days after May 5” and the Outlook calendar will do the calculation and create the event for that day.  You can adjust if necessary if it lands on a weekend or holiday. This works in Outlook Tasks as well.

 Mobile Apps

‎Voice Activated Assistants

Just ask Siri or Alexa or the Google Assistant: “Hey Google, what is 30 days from May 2, 2021?” or “Alexa, tell me the date 56 days after 16th March.” You can ask Siri, “How many days between October 31, 2021 and December 12, 2021? “


Time and Date –

With options to add or subtract days from a date or find a duration between two times and dates, plus filters for workdays (exclude weekends and public holidays) this free website fits the bill for many lawyers.

Wolfram|Alpha –

Not as functional as the Time and Date website, the Wolfram|Alpha Date Difference Calculator, does show results in time span (weeks, days, weekdays), and time difference from today even if your date ranges are in the future (handy for setting up ticklers).

Google Instant Results –

Just type “days between May 2 and June 5” or “[number] days from [date]” and Google will give you the information in instant results, meaning you don’t have to go to a website to get the answer!

Rules Based Calendaring

If you want help determining dates based on court rules, with ticklers and other features, there are any number of legal specific applications that you can purchase. Some are available in practice management software; others are available as “stand alone” products that integrate with your MS Outlook or Google Workspace calendar or practice management application. Check with your practice management application provider to see if rules-based calendaring is available as an add-on or an upgrade. Below are some options for stand-alone programs.

Law Toolbox – Court Date Calendaring, Court Deadline Calculator & DMS

Law Toolbox is available as an integration with nine practice management applications, plus deep integration with MS Outlook and Teams. They also integrate with Apple, Lotus Notes, DocuSign, and more. In addition to calendaring, Law Toolbox’s integrations with MS 365 extends functions like matter management, document management and video conferencing through the Microsoft suite. Pricing is based on number of users. charges by number of cases and has been on the market for quite some time. Formerly part of Compulaw, it is now available through Aderant (who also offers Compulaw). calculates court dates, applies court rule changes with notification and lets you run reports and offers different views. It integrates with MS Outlook or you can import iCal files into the calendar of your choice.

Calendar Rules

Calendar Rules integrates with over 20 calendar/docket/practice management systems as well as MS 365 and Outlook. You can also calculate dates, dockets and perform docket research directly from the website. Pricing is based on the rules sets you subscribe to and you can get a quote by filling out the form on their website.


Whether you ask Google, check a website or app, or pay for rules-based calendaring always remember to double (triple) check your date calculations. Malpractice applications often ask about your method for checks and balances for calendaring, with the preference leaning towards human review of deadlines by more than one person. Use the tools but know that court rules, unique jurisdictional holidays, and the specific trigger date may affect the calculation so be prepared. Trust, but verify.