19 frontier AI models still put Calgary on standard time after Alberta dropped DST

A developer benchmarked 19 frontier AI models on time zone knowledge after Alberta stopped changing its clocks in June 2026. All 19 wrongly said 11:00 instead of 10:00 for Calgary on November 15. The 122-question benchmark, graded against tzdata 2026d, dated each model's knowledge to months or years behind current time zone rules.

• All 19 models answered 11:00 instead of 10:00 for Calgary on Nov 15
• Best score: GPT-6 Astra with 107 of 122 questions correct
• Worst score: Claude Haiku 4.5 with 59 of 122
• 46 questions changed answers across tzdata releases since 2022