Days

gaspatchio_core.accessors.excel_functions.days.days(end_date, start_date)

Calculate the number of days between two dates, similar to Excel's DAYS.

Returns the number of days between a start date and an end date as an integer. The result is positive if the end date is after the start date, and negative if the end date is before the start date.

When to use

• Policy Duration Calculations: Determine the exact number of days a policy has been in force for premium calculations or exposure analysis.
• Claim Processing Time: Calculate the number of days between claim filing and settlement for service level tracking.
• Grace Period Tracking: Measure the number of days in grace periods for lapsed policies or late premium payments.
• Interest Accrual: Calculate the exact number of days for interest calculations on policy loans or reserves.
• Waiting Period Compliance: Track waiting periods in days for specific benefits or coverage exclusions.
• Performance Metrics: Measure time-to-issue, underwriting duration, or other process timelines in days.

Parameters

end_date : IntoExprColumn The ending date of the period. Can be a scalar date, a column of dates, or a list column of dates. start_date : IntoExprColumn The starting date of the period. Can be a scalar date, a column of dates, or a list column of dates.

Returns

pl.Expr A Polars expression containing the number of days as Int64 (or List[Int64] for list columns). The result is end_date - start_date.

Examples

Scalar Example: Policy Duration in Days

import datetime
from gaspatchio_core import ActuarialFrame

data = {
    "policy_id": ["P001", "P002", "P003"],
    "issue_date": [
        datetime.date(2023, 1, 15),
        datetime.date(2023, 3, 1),
        datetime.date(2023, 6, 10)
    ],
    "valuation_date": [
        datetime.date(2023, 12, 31),
        datetime.date(2023, 12, 31),
        datetime.date(2023, 12, 31)
    ],
}
af = ActuarialFrame(data)

af.days_in_force = af.valuation_date.excel.days(af.issue_date)

print(af.collect())

shape: (3, 4)
┌───────────┬────────────┬────────────────┬───────────────┐
│ policy_id ┆ issue_date ┆ valuation_date ┆ days_in_force │
│ ---       ┆ ---        ┆ ---            ┆ ---           │
│ str       ┆ date       ┆ date           ┆ i64           │
╞═══════════╪════════════╪════════════════╪═══════════════╡
│ P001      ┆ 2023-01-15 ┆ 2023-12-31     ┆ 350           │
│ P002      ┆ 2023-03-01 ┆ 2023-12-31     ┆ 305           │
│ P003      ┆ 2023-06-10 ┆ 2023-12-31     ┆ 204           │
└───────────┴────────────┴────────────────┴───────────────┘

Vector Example: Monthly Projection Days

import datetime
import polars as pl
from gaspatchio_core import ActuarialFrame
from gaspatchio_core.accessors.excel_functions.days import days

data = {
    "policy_id": ["P001", "P002"],
    "projection_dates": [
        [datetime.date(2024, 1, 1), datetime.date(2024, 2, 1), datetime.date(2024, 3, 1)],
        [datetime.date(2024, 1, 15), datetime.date(2024, 2, 15), datetime.date(2024, 3, 15)]
    ],
    "issue_date": [datetime.date(2024, 1, 1), datetime.date(2024, 1, 1)]
}
af = ActuarialFrame(data)

af.days_from_issue = af.projection_dates.list.eval(
    days(pl.element(), pl.lit(datetime.date(2024, 1, 1)))
)

print(af.collect())

shape: (2, 4)
┌───────────┬──────────────────────────────────────┬────────────┬─────────────────┐
│ policy_id ┆ projection_dates                     ┆ issue_date ┆ days_from_issue │
│ ---       ┆ ---                                  ┆ ---        ┆ ---             │
│ str       ┆ list[date]                           ┆ date       ┆ list[i64]       │
╞═══════════╪══════════════════════════════════════╪════════════╪═════════════════╡
│ P001      ┆ [2024-01-01, 2024-02-01, 2024-03-01] ┆ 2024-01-01 ┆ [0, 31, 60]     │
│ P002      ┆ [2024-01-15, 2024-02-15, 2024-03-15] ┆ 2024-01-01 ┆ [14, 45, 74]    │
└───────────┴──────────────────────────────────────┴────────────┴─────────────────┘