---
title: "Day count conventions supported by LUSID"
slug: "day-count-conventions-supported-by-lusid"
tags: ["day count convention"]
updated: 2026-05-03T08:05:05Z
published: 2026-05-03T08:05:05Z
canonical: "support.lusid.com/day-count-conventions-supported-by-lusid"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://support.lusid.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Day count conventions supported by LUSID

You must specify a *day count convention* when you create a [flow convention and/or an index convention](/v1/docs/flow-conventions-and-index-conventions) to calculate a precise number of days between two dates.

The number of days helps determine how much gets paid in cashflows distributed by certain types of instrument.

Note the following:

- If you specify an alias name (see table below), LUSID stores and returns the primary name. For example, if you create a flow convention with `dayCountConvention` set to `Act360` then LUSID stores and returns `Actual360`.
- You must specify a [tenor](/v1/docs/specifying-tenors-in-lusid) for the `paymentFrequency` field that LUSID uses to determine the number of payments per year, so for example a tenor of:
  - `1M` yields twelve payments per year
  - `3M` yields four payments per year
  - `6M` yields two payments per year
  - `12M` or `1Y` yields one payment per year, and so on.
- You have the option to specify `paymentCalendars` to exclude non-business days from calculations. If no calendars are specified, holidays and weekends are included.

| Primary name | Alias name | Accrued days (numerator) | Days in period (denominator) | [Accrual factor](/v1/docs/how-does-lusid-calculate-accrued-interest) | Notes |
| --- | --- | --- | --- | --- | --- |
| `Act252` |  | Actual number of days based on `paymentCalendars` | 252 / Payments per year | Accrued days / Days in period |  |
| `Act364` |  | Actual number of days based on `paymentCalendars` | 364 / Payments per year | Accrued days / Days in period |  |
| `Act365_25` |  | Actual number of days based on `paymentCalendars` | 365.25 / Payments per year | Accrued days / Days in period |  |
| `Act365Cad` |  | Actual number of days based on `paymentCalendars` | 365 / Payments per year | If Accrued days > 365 / Payments per year Then: 1 - [(Days in period - Accrued days) * Payments per year / 365] Else: Accrued days / Days in period | With this day count convention, accrued interest can never exceed the coupon amount |
| `Act365F` |  | Actual number of days based on `paymentCalendars` | 365 / Payments per year | Accrued days / Days in period |  |
| `Act365L` |  | Actual number of days based on `paymentCalendars` | 365 / Payments per year or 366 / Payments per year | Accrued days / Days in period | If part of the accrual period is during a leap year (whether it contains 29 February or not), Days in period is 366 / Payments per year |
| `ActActAFB` |  | Actual number of days based on `paymentCalendars` | 365 / Payments per year or 366 / Payments per year | Accrued days / Days in period | If the accrual period contains 29 February, Days in period is 366 / Payments per year |
| `ActActIsma` | `ActActIcma` | Actual number of days based on `paymentCalendars` | Actual number of days based on `paymentCalendars` / Payments per year | Accrued days / Days in period |  |
| `Actual360` | `Act360`, `MoneyMarket` | Actual number of days based on `paymentCalendars` | 360 / Payments per year | Accrued days / Days in period |  |
| `Actual365` | `Act365` | Actual number of days based on `paymentCalendars` | 365 / Payments per year | Accrued days / Days in period |  |
| `ActualActual` | `ActAct`, `ActActIsda` | Actual number of days based on `paymentCalendars` | Actual number of days based on `paymentCalendars` / Payments per year | Accrued days / Days in period |  |
| `Bus252` |  | Actual number of business days based on Brazilian calendar | 252 / Payments per year | Accrued days / Days in period | For the business days, the Brazilian calendar is used. |
| `NL360` |  | Actual number of days based on `paymentCalendars` without including leap days | 360 / Payments per year | Accrued days / Days in period | If 29 February is included in the accrual period, it is not taken into account |
| `NL365` |  | Actual number of days based on `paymentCalendars` without including leap days | 365 / Payments per year | Accrued days / Days in period | If 29 February is included in the accrual period, it is not taken into account |
| `OneOne` |  | 1 | 1 | 1 | Meaningful for zero-coupon bonds with a payment frequency equal to `1T` |
| `Thirty360` | `ThirtyU360`, `Bond` | Each month is assumed to have 30 days | 360 / Payments per year | Accrued days / Days in period |  |
| `Thirty365Isda` |  | Each month is assumed to have 30 days | 360 / Payments per year | Accrued days / Days in period |  |
| `ThirtyActIsda` |  | Each month is assumed to have 30 days | Actual number of days based on `paymentCalendars` / Payments per year | Accrued days / Days in period |  |
| `ThirtyE360` | `EuroBond` | Each month is assumed to have 30 days except if the maturity date is the last day of February, when the actual number of days in February is used | 360 / Payments per year | Accrued days / Days in period |  |
| `ThirtyE360Isda` |  | Each month is assumed to have 30 days except February, when the actual number of days in February is used | 360 / Payments per year | Accrued days / Days in period |  |
| `ThirtyE365Isda` |  | Each month is assumed to have 30 days except February, when the actual number of days in February is used | 365 / Payments per year | Accrued days / Days in period |  |
| `ThirtyEActIsda` |  | Each month is assumed to have 30 days except February, when the actual number of days in February is used | Actual number of days based on `paymentCalendars` / Payments per year | Accrued days / Days in period |  |
| `ThirtyU360EOM` |  | Each month is assumed to have 30 days with special treatments on day-of-month 31 and for February: - If both dates are the last day of February, maturity date day is changed to 30. - If only the start date is the last day of February, start date day is changed to 30. - If maturity date day is 31 and start date day is either 30 or 31 then maturity date day is changed to 30. - If start date day is 31 then start date day is changed to 30. | 360 / Payments per year | Accrued days / Days in period |  |