Illustration: Sarah Grillo/Axios

When the popular free-stock-trading app Robinhood went offline Monday and Tuesday, Twitter wags immediately opined that programmers must have failed to account for this year's quadrennial Leap Day, which fell on Saturday. The firm eventually denied that scenario, pinning the crash on simple infrastructure overload.

The big picture: But it wasn't a bad guess. Calendar quirks have always been a predictable source of software bugs. We think of the measurement of time as a science, but it is also a human art, encrusted with customs, exceptions and historical quirks.

  • Time zones are irregular.
  • Times are a.m. and p.m. except when they're on a 24-hour clock.
  • Different countries format dates differently.
  • To remember how many days each month has, people need mnemonic rhymes!
  • Computers are great at keeping track of all these things, but the people who program them still make goofs trying to account for all of the cases.

Y2K: Two decades ago, a bug associated with the flip of the millennium counter threatened a Y2K doomsday that never materialized, whether because the danger had been overhyped or because freaked-out companies hauled enough COBOL programmers out of retirement to fix everything.

2038: Today, Unix programmers are already preparing for the "Year 2038 bug." Some versions of Unix will break in that year as the number of seconds that have passed since Unix time began in 1970 grows too big to hold in a 32-bit register.

Daylight savings time: The clock's seasonal adjustments used to cause many systems to throw fits. Modern systems handle them smoothly, for the most part — but every time the clocks move forward or back, the brains of your local sysadmins, IT crews, and tech-support teams ache from their old war wounds.

What's next: The U.S. moves its clocks forward this coming weekend. Everybody ready?

Go deeper

Trump commutes Roger Stone's sentence

Roger Stone arriving at his sentencing hearing on Feb. 20. Photo: Drew Angerer/Getty Images

President Trump on Friday evening commuted the sentence of his longtime associate Roger Stone, according to two senior administration officials. Stone in February was sentenced to 40 months in prison for crimes including obstruction, witness tampering and making false statements to Congress.

Why it matters: The controversial move brings an abrupt end to the possibility of Stone spending time behind bars. He had been scheduled to report to prison on July 14.

Updated 4 hours ago - Health

Which states have set single-day coronavirus records this week

Data: COVID Tracking Project and state health department data compiled by Axios; Map: Danielle Alberti and Naema Ahmed/Axios

13 states this week surpassed records set just last week for their highest number of coronavirus infections in a single day, according to the COVID Tracking Project and state health department data. 16 states in total reported new highs.

The big picture: The United States' alarming rise in coronavirus cases isn't just due to increased testing — particularly where the number of cases has grown fastest over the last month, Axios' Andrew Witherspoon and Caitlin Owens report.

Updated 4 hours ago - Politics & Policy

Coronavirus dashboard

Illustration: Sarah Grillo/Axios

  1. Global: Total confirmed cases as of 6:30 p.m. ET: 12,389,660 — Total deaths: 557,279 — Total recoveries — 6,830,596Map.
  2. U.S.: Total confirmed cases as of 6:30 p.m. ET: 3,169,611 — Total deaths: 133,885 — Total recoveries: 983,185 — Total tested: 38,856,341Map.
  3. Public health: The reality of the coronavirus bites.
  4. Trade: Trump says he's no longer considering phase-two trade deal with China because the pandemic damaged the two countries' relationship.
  5. 🎧 Podcast: Rural America has its own coronavirus problem.