ConvertTimezone

convertTimezone shifts a timestamp into a specified time zone by adding or subtracting the right interval from the timestamp.

Timestamps and time zones are rather nasty to work with (it’s easy to make mistakes, and difficult to catch them), so you should only try to use convertTimezone if the interpretation of your data is sensitive to time-based cutoffs.

For example, if you’re tracking user logins over time, you probably won’t run your business differently if some logins get counted on Mondays instead of Tuesdays. However, if you’re using Metabase to do something precise, like your taxes, you (and the government) will probably care a lot more about the difference between transactions that occurred on Dec 31 vs. Jan 1.

Parameters

column can be any of:

• The name of a timestamp column,
• a custom expression that returns a timestamp, or
• a string in the format "YYYY-MM-DD or "YYYY-MM-DDTHH:MM:SS".

target:

• The name of the time zone you want to assign to your column.

source:

• The name of your column’s current time zone.
• Required for columns or expressions with the data type timestamp without time zone.
• Optional for columns or expressions with the data type timestamp with time zone.
• For more info, see Accepted data types.

We support tz database time zone names (such as “Canada/Eastern” instead of “EST”).

Creating custom report dates

Let’s say that you have some time series data that’s stored in one or more time zones (Source Time). You want to create custom reporting dates for a team that lives in EST.

If Source Time is stored as a timestamp with time zone or a timestamp with offset, you only need to provide the target time zone:

convertTimezone([Source Time], 'EST')

If Source Time is stored as a timestamp without time zone, you must provide the source time zone (which will depend on your database time zone):

convertTimezone([Source Time], 'EST', 'UTC')

It’s usually a good idea to label convertTimezone columns with the name of the target time zone (or add the target time zone to the metadata of a model). We promise this will make your life easier when someone inevitably asks why the numbers don’t match.

If you’re not getting the results that you expect:

• Check if you have the right source time zone.
• Ask your database admin about timestamp with time zone vs. timestamp without time zone (for more info, see Accepted data types).

Choosing a source time zone

When you’re doing time zone conversions, make sure you know the source time zone that you’re working with. Different columns (and even different rows) in the same table, question, or model can be in different “source” time zones.

For example, say you have a table with one row for each person who visited your website. It’s hard to tell, just from looking at December 28, 2022, 12:00 PM, whether the “raw” timestamp is:

• stored using your database’s time zone (usually UTC),
• stored without time zone metadata (for example, if the website visitor is in HKT, then the timestamp December 28, 2022, 12:00 PM might “implicitly” use Hong Kong time),
• displayed in your Metabase report time zone.

For more gory details, see Limitations.

Accepted data types

We use “timestamp” and “datetime” to talk about any temporal data type that’s supported by Metabase.

If your timestamps are stored as strings or numbers in your database, an admin can cast them to timestamps from the Table Metadata page.

To use convertTimezone without running into errors or pesky undetectable mistakes, you should know that there are a few varieties of timestamp data types:

Note that the first part of the timestamp is in UTC (same thing as GMT). The time zone or offset tells you how much time to add or subtract for a given time zone.

convertTimezone will work with all three types of timestamps, but the output of convertTimezone will always be a timestamp without time zone.

Limitations

convertTimezone is currently unavailable for the following databases:

• Amazon Athena
• Databricks
• Druid
• MongoDB
• Presto
• SparkSQL
• SQLite
• Metabase Sample Database

Notes on source time zones

Metabase displays timestamps without time zone or offset information, which is why you have to be so careful about the source time zone when using convertTimezone.

The Metabase report time zone only applies to timestamp with time zone or timestamp with offset data types. For example:

The Metabase report time zone will not apply to the output of a convertTimezone expression. For example:

convertTimezone("2022-12-28T12:00:00 AT TIME ZONE 'Canada/Central'", "Canada/Pacific", "Canada/Central")

will produce a raw timestamp without time zone

2022-12-28T04:00:00

and displayed in Metabase as

Dec 28, 2022, 4:00 AM

If you use convertTimezone on a timestamp without time zone, make sure to use ‘UTC’ as the source time zone, otherwise the expression will shift your timestamp by the wrong amount. For example, if our timestamp without time zone is only “implied” to be in CST, we should use ‘UTC’ as the source parameter to get the same result as above.

For example, if we choose ‘CST’ as the source time zone for a timestamp without time zone:

convertTimezone("2022-12-28T12:00:00", "Canada/Pacific", "Canada/Central")

we’ll get the raw timestamp without time zone

2022-12-28T10:00:00

displayed in Metabase as

Dec 28, 2022, 10:00 AM

Related functions

This section covers functions and formulas that work the same way as the Metabase convertTimezone expression, with notes on how to choose the best option for your use case.

• SQL
• Spreadsheets
• Python

SQL

When you run a question using the query builder, Metabase will convert your graphical query settings (filters, summaries, etc.) into a query, and run that query against your database to get your results.

If our timestamp sample data is a timestamp without time zone stored in a PostgreSQL database:

SELECT source_time::TIMESTAMP AT TIME ZONE 'UTC' AT TIME ZONE 'EST' AS team_report_time_est

is the same as the convertTimezone expression with a source parameter set to ‘UTC’:

convertTimezone([Source Time], "Canada/Eastern", "UTC")

If source_time is a timestamp with time zone or timestamp with offset (for example, in a Snowflake database), then we don’t need to specify a source time zone in SQL or in Metabase.

SELECT convert_timezone('America/Toronto', source_time) AS team_report_time_est

is the same as

convertTimezone([Source Time], "Canada/Eastern")

Remember that the time zone names depend on your database. For example, Snowflake doesn’t accept most time zone abbreviations (like EST).

Spreadsheets

If our timestamp sample data is in a spreadsheet where “Source Time” is in column A, we can change it to EST by subtracting the hours explicitly:

A1 - TIME(5, 0, 0)

to get the same result as

convertTimezone([Client Time], "Canada/Eastern")

Python

If the timestamp sample data is stored in a pandas dataframe, you could convert the Source Time column to a timestamp object with time zone first(basically making a timestamp without time zone into a timestamp with time zone), then use tz_convert to change the time zone to EST:

df['Source Time (UTC)'] = pd.to_timestamp(df['Source Time'], utc=True)
df['Team Report Time (EST)'] = df['Source Time (UTC)'].dt.tz_convert(tz='Canada/Eastern')

to do the same thing as a nested convertTimezone expression

convertTimezone(convertTimezone([Source Time], "UTC"), "Canada/Eastern", "UTC")

Further reading

• Custom expressions documentation
• Custom expressions tutorial
• Time series analysis