--- title: "Day count conventions supported by LUSID" slug: "day-count-conventions-supported-by-lusid" 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 | |