Hi.
You can use navigation parameters.
navigation: {
initialDisplayUnit: "1 d",
initialDisplayPeriod: "7 d",
//initialDisplayAnchor: ...
}
Here is a reference to our documentation navigation.initialDisplayPeriod :
https://zoomcharts.com/developers/en/time-chart/api-reference/settings.html#doc_navigation.initialDisplayPeriod
Also you should use initialDisplayAnchor as by default it uses "newestData", meaning that last 7 days will be calculated from latest data point timestamp. Change it accordingly for your needs.
https://zoomcharts.com/developers/en/time-chart/api-reference/settings.html#doc_navigation.initialDisplayAnchor
UPDATE:
Another property should be considered:
timeAxis.maxUnitWidth
Currently the default value is 200, meaning that if you have a wide TimeChart and you want to display only 7 units, then each unit will take not more than 200px of space. In such case you should increase this value accordingly.