For developers relying on automated workflows, timing precision is non-negotiable. Recently, users of Anthropic\u2019s Claude Code encountered a peculiar bug tied to the transition out of daylight saving time (DST). Specifically, the system\u2019s scheduled tasks and internal loops were behaving erratically during the “repeated hour”-the period when clocks fall back, effectively creating a duplicate hour in the local timeline.<\/p>\n
\nThe issue manifested in two distinct ways: tasks were either triggering prematurely or executing repeatedly after every turn. It is important to clarify that this was not a simple case of a job running twice; rather, the logic governing the task scheduler was misinterpreting the temporal overlap caused by the clock shift. <\/p>\n
In software engineering, handling the “fall back” hour is a notorious edge case. When a system clock resets, any process relying on absolute time intervals can become desynchronized. For instance, if a background process is set to poll an API every 60 minutes, the sudden shift in the system clock can cause the scheduler to perceive the repeated hour as a trigger to re-run pending tasks immediately, leading to the “firing again” behavior observed by users.<\/p>\n