# Number of Days In A Period Using [ACT] --- Remember Leap Years

Development Team Montego Data Limited
September 2003

#### Requires

• Brief Calendar Knowledge

Introduction
Conclusion

## Introduction

If Buying 5 contracts with a price of 80 the phrase is '80 for 5'
If Selling 5 contracts with a price of 80 the phrase is '5 at 80'

Fixed Income Arithmetic
The Money Market convention is Act/360 which means dividing the actual number of days in the period by 360.
The market price compensates for this convention as no year has 360 days.

 Percent Terms Currencies 4.5% Act/360 USD JPY EUR 4.5625% Act/365 GBP ZAR

The sum is : 4.5% / 360 == 4.5625% / 365 == 0.0125

Proportion Of The Year
From 20 August 2003 to 20 Feb 2004 is a period of six months
In this period 01 Jan 2004 to 20 Feb 2004 is 51 days in a 366 day year
In this period 20 Aug to 20 Feb there are 184 days
So you can say 184 / 365
Or ( 51 * 366 + 133 * 365) / 184 = 365.26 days and year proportion 184 / 365.26 = 0.5037 of a year.
What clearly matters when dealing with ACT/365 is to follow the same rules in a leap year !!

## Conclusion

There is always another subtle issue to consider.