Date Range Comparisons in Data Studio: Previous Period vs Previous Year

• Previous period
• Previous year
• Rules I follow
• Checking it works

Comparison numbers are often the first thing a reader looks at in a Data Studio (formerly Looker Studio) report, and the easiest thing to get wrong. I’m Harsh Khubchandani, an independent Data Studio consultant based in New Delhi, and this is how I set them up on client reports.

§Previous period

Previous period compares against the same number of days immediately before. It works well for short, steady trends like last 7 days. It works badly across months of different lengths or seasonal swings.

§Previous year

Previous year compares against the same dates a year earlier. I use it for seasonal businesses such as retail, travel and education, where last month means little without last year’s context.

§Rules I follow

• Pick one comparison per scorecard and say which in the chart title.
• Align weekdays when daily patterns matter, using a custom comparison range.
• Avoid comparisons that include today, because the current day is incomplete.
• Show the absolute change next to the percentage when base numbers are small.

§Checking it works

Before handover I switch the report to a few different date ranges and confirm the comparison arrows still point the right way. A comparison that only works for one month causes more confusion than having none.

Clear comparisons are part of what I look at in a free 30-minute report review. Details at https://datastudioconsultant.com/