BigQuery convert unix timestamp struct to struct of datetime - struct

Question

I have a BigQuery table that contains a struct column called daySliderTimes in the following form:
daySliderTimes STRUCT<_field_1 STRUCT<_seconds INT, _nanoseconds INT>, _field_1 STRUCT<_seconds INT, _nanoseconds INT>.
_field_1 and _field_2 represent two different timestamps. _seconds and _nanoseconds represent time since the unix epoch.
I want to convert the data into a new STRUCT with the following form:
daySlidertimes STRUCT<startTime DATETIME, endTime DATETIME>
This is the table as seen in the BigQuery UI:

Answer 1

If you want to create a new table from the old one with the format daySlidertimes STRUCT<startTime DATETIME, endTime DATETIME>, you can cast the data in milliseconds and so then transform it to TIMESTAMP with the function "TIMESTAMP_MICROS", check this link to see the amount of functions to parse timestamp [1].
An example of the query should look something like this:
CREATE TABLE `project.dataset.new_table` AS
SELECT searchDocId,
STRUCT(TIMESTAMP_MICROS(CAST(
((daySliderTimes.field1.seconds * 1e+6) +
ROUND(daySliderTimes.field1.nanoseconds * 0.001)) AS INT64)) as
startTime,
TIMESTAMP_MICROS(CAST( ((daySliderTimes.field2.seconds * 1e+6) +
ROUND(daySliderTimes.field2.nanoseconds * 0.001)) AS INT64)) as endTime)
as daySliderTimes,
enabledDaySliders
FROM `project.dataset.old_table`
[1] https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#parse_timestamp

Answer 2

You can use TIMESTAMP_SECONDS() function. This function converts the seconds to DATETIME format.
Therefore, you are ale to transform daySliderTimes._field_1.seconds to a date using TIMESTAMP_SECONDS() function. As well as, for _field_2, then aggregate them in a new struct format.
During the creation of the view or table, in your select you can do the following:
WITH table_newStruct as(
SELECT
#Select all the desired fields
searchDocId,
STRUCT(TIMESTAMP_SECONDS(daySliderTimes._field_1.seconds) as startTime,
TIMESTAMP_SECONDS(daySliderTimes._field_.seconds) as endTime) as new_daySlidertimes
FROM 'table_source')
SELECT searchDocId, new_daySlidertimes
FROM 'table_newStruct'
In addition, the returned TIMESTAMP should be in the following format 1970-01-01 00:00:00 UTC. You can format it using the FORMAT_DATE() function.