Daylight Savings Time (DST)

Twice a year we shift time... and frustrate clinical timekeeping. On March 9, 2025, clocks turn forward 1 hour at 02:00 to become 03:00. Then, on November 2, 2025, clocks turn backward 1 hour at 02:00 to become 01:00. 

Clinicians need to be aware of these shifts and unique implications for clinical information system (CIS) behaviours. While ambulatory care is little affected by what happens in the early hours of the morning, emergent, inpatient, surgical and critical care contexts can be sensitive to the loss or gain of small time intervals. Linked at the bottom of this page, 1-pagers summarize key considerations around DST for prescribers, and guides provide further details.

Spring Forward (March)

Patients undergoing time-sensitive or time-limited therapies (e.g., continuous infusion of fluids or medications for a specified interval) are at risk for receiving a smaller intervention exposure than expected. Treatments or tests scheduled for the "skipped" hour need careful attention to ensure that they occur, are sequenced and are not co-administered if meant to be separated in time.

Critical Situations and Downtime Procedures

• • Anesthesia and Intensive Care contexts may need to document on paper for time-sensitive activities (calculated totals will be larger than actual totals, anesthesia start and stop times may be off by an hour, etc.) immediately before and after the DST shift.

    • Consider whether there are multiple continuous infusions that are time-sensitive, whether attached devices might mis-report data collection times, and whether back-documenting would be safer for a particular patient care scenario. Back-documenting from temporary paper records gives time to carefully consider medication volumes and exposure times. 

Patient Tracking and Event-to-Event Timing

• • Times spanning the time change appear one hour longer than they should be. For example, time to antibiotic administration, total ER visit times, or hours since consultation request will display longer than experienced.

  • --> Take the non-existent hour into account if time intervals affect clinical choices in the early morning hours.

Volume Administration Calculations

• • While built-in warnings will recognize the time change, be wary of the appearance of more volume or duration continuous administrations than the patient actually experiences.

  • Nursing teams receive instruction about how the CIS will prevent scheduling of tasks during the non-existent hour.

  • --> It may be necessary to continue infusions for what appears to be an extra hour.

Scheduled Medications

• • The CIS will automatically reschedule any medication or test with a due time falling in the non-existent 02:00-03:00.

  • Due times before 02:00 and after 04:00 are not adjusted. This could mean that frequently administered medications are given at a tighter interval than expected.

  • Order entry tools are DST-aware and will prompt the user to confirm intentions when an order spans DST. Nonetheless, clinicians should exercise extra caution at this time.

Graphs and Flowsheets

• • Timeline displays (graphs) for Results Review, Synopsis, Flowsheets and some Reports will show the 02:00-03:00 interval even though it did not occur. Clinicians should bear this in mind when interpreting trends.

Decision Supports

• • Decision support alerts that fire if, for example, a medication is ordered too soon after a prior administration may be falsely negative around the time of the DST shift. A warning to not administer within a 1-hour interval could fail to fire because the underlying algorithm may not be sensitive to the missed hour.