The files are prepended in the __manifest__.py file:
```
'assets': {
'spreadsheet.o_spreadsheet': [
('prepend', 'spreadsheet_dates/static/src/helpers_constants.js'),
('prepend', 'spreadsheet_dates/static/src/global_filters_helpers.js'),
],
}
```

Then in helpers_contants.js:
```
import { patch } from "@web/core/utils/patch";
import { _t } from "@web/core/l10n/translation";

patch(require('@spreadsheet/helpers/constants'), {
RELATIVE_DATE_RANGE_TYPES: [
{ type: "year_to_date", description: _t("Year to Date") },
{ type: "last_week", description: _t("Last 7 Days") },
{ type: "last_month", description: _t("Last 30 Days") },
{ type: "last_three_months", description: _t("Last 90 Days") },
{ type: "last_six_months", description: _t("Last 180 Days") },
{ type: "last_year", description: _t("Last 365 Days") },
{ type: "last_three_years", description: _t("Last 3 Years") },
{ type: "o_last_business_day", description: _t("Last Business Day") },
{ type: "o_last_week", description: _t("Last Week") },
{ type: "o_last_month", description: _t("Last Month") },
]
});
```

And global_filters_helpers.js
```
import { patch } from "@web/core/utils/patch";
import { serializeDate, serializeDateTime } from "@web/core/l10n/dates";
import { Domain } from "@web/core/domain";

var helpers = require('@spreadsheet/global_filters/helpers');
var _super = helpers.getRelativeDateDomain;
patch(helpers, {
getRelativeDateDomain(now, offset, rangeType, fieldName, fieldType) {
var s = _super(...arguments)
// Do stuff if _super returns none
}
});
```

I got it to work, thank you so much!