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  • Your Data Isn’t Wrong. Your Timezone Is. (UTC vs Local Explained Before It Breaks Your Dashboard)

Your Data Isn’t Wrong. Your Timezone Is. (UTC vs Local Explained Before It Breaks Your Dashboard)

Rather than blaming the algorithm, pipeline, or analyst... consider this question: Are you looking at your data in Universal Time (UTC) or Local Time (LT)?

Read time: 2.5 minutes

Dead on arrival! Every day for a period of three hours, there is a dip in revenue from your dashboard. Slack was flooded with questions and chatter. “Was checkout having issues?” “Have the marketers stopped running campaigns?” “Maybe the models are degrading?”

As the blood pressure of all employees rose, the culprit became clear after 45 minutes: System A logs events in UTC, but the report shows them in LT. No systems were broken, except for the employees' blood pressure. Time zone confusion does not only occur with travelers. It happens with data as well!

How to Stop Getting Confused about UTC and your LT?

1. Store in UTC.
Your database should store all timestamps in UTC. Convert to local only at display time.

2. Clearly indicate which timezone the timestamps are in.
In your dashboards, indicate with a label, for instance, "All Times displayed are in UTC" or "All Times displayed are in Local Time."

3. Store timezone information as metadata.
If you sell to customers in different time zones worldwide, you'll want to save this information to avoid chaos in later reporting.

4. Be Aware of DST Shifts.
Shifts in daylight saving time (DST) can create major issues with regard to daily aggregate data and scheduled jobs.

5. Before making Comparisons, Get Both Systems Aligned to the Same Timestamp Format
When using two systems to pull reports or analyze data trends, be sure both have their timestamps normalized to ensure valid comparisons.

Poorly written content can create very misleading analytical data due to even small time zone differences.

💡Key Takeaway: 

When suspicious-looking numbers show up in a data set, check the clock before checking the code. Utilizing local time or UTC time has derailed more dashboards than bad models ever did. In data, timing is not only everything, but it's also the very first thing.

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