What is the "30E/360 ISDA" Day Count Convention?

30E/360 ISDA - 30E/360 ISDA is a Day Count Convention mainly used for German corporate bonds.

30E/360 ISDA is also referred as 30/360 German, 30E/360 German, German, Eurobond basis (ISDA 2000).

30E/360 ISDA can be formally defined as:

Day_Count_Factor(Y1,M1,D1,Y2,M2,D2)
   = DiR(Y1,M1,D1,Y2,M2,D2) / DiY(Y1,M1,D1,Y2,M2,D2)

DiR(Y1,M1,D1,Y2,M2,D2) = 360×(Y2-Y1) + 30×(M2-M1) + (D2-D1)
  where D1 and D2 are adjusted as below:
    If T1 is End of Month, set D1 = 30;
    If T2 is End of Month, 
      except it's End of February and the Maturity Date, set D2 = 30.

DiY(Y1,M1,D1,Y2,M2,D2) = 360

where: 
  T1 = (Y1,M1,D1): Starting date (inclusive)  
  T2 = (Y2,M2,D2): Ending date (exclusive) of the Accrual Range  
  T3 = (Y3,M3,D3): Ending date (exclusive) of the Accrual Period 
  T4 = (Y4,M4,D4): Ending date (exclusive) of the Accrual Year 

Example:
   2026-01-01   2025-01-16   2026-02-01            2027-01-01
---T1-----------T2-----------T3-----------...------T4--- 

  [T1-----------T2): Accrual Range
  [T1------------------------T3): Accrual Period
  [T1-------------------------------------...------T4): Accrual Year

30E/360 ISDA Convention always resets last day of month to 30th day for the starting date, and resets last day of month to 30th day for the ending date (except the ending date is last day of February the Maturity Date).

Here is an example of DekaBank bond security.

ISIN:                   DE000DK0VRA2
Issuer:                 DekaBank
Interest rate:          1.35%
Interest frequency:     Annually (1 time in a year)
Day Count Convention:   30E/360 ISDA
Term:                   25 Years 
  Start Date:           2019-11-15
  Maturity Date:        2044-11-15

If you bought $1,000.00 of this FHLB bond, here is how you can calculate Accrued Interest in the date range of [T1,T2) = [2025-11-15, 2026-02-15):

T1 = 2025-11-15: Starting date (inclusive)
T2 = 2026-02-15: Ending date (exclusive) of the Accrual Range 
T3 = 2026-11-15: Ending date (exclusive) of the Accrual Period  
T4 = 2026-11-15: Ending date (exclusive) of the Accrual Year

DiR(Y1,M1,D1,Y2,M2,D2) = 360×(Y2-Y1) + 30×(M2-M1) + (D2-D1)
  = 360×(2026-2025) + 30×(2-11) + (15-15)
  = 90 

DiY(Y1,M1,D1,Y2,M2,D2) = 360

Day_Count_Factor(T1,T2) = DiR(T1,T2) / DiY(T1,T2)
  = 90 / 360 
  = 0.25

Accrued_Interest = Principal × Interest_Rate × Day_Count_Factor
  = $1,000.00 × 1.35% × 0.25
  = $3.375
  = $3.38

30E/360 ISDA convention has several main properties. See next tutorials for more details.

• The Day Count Factor for a whole regular Accrual Period is a constant.
• A fixed amount of Accrued Interest is paid out for each Accrual Period:
• Daily Interest Rate is a fixed value independent of Accrual Periods.
• If End of Month (EOM) is on 31th, no Accrued Interest is given on the 30th.
• If End of Month (EOM) is in February, 2-day or 3-day Accrued Interest is given on the day before EOM.
• Not applicable for daily Compound Interest.
• Day Count Factor is additive for consecutive and non-overlapping Accrual Ranges.

References:

• DekaBank Dt.GirozentraleFestzins-Anleihe v.2019(29/44), Business Insider.

⇒ "30E/360 ISDA" - Rules Expressed Differently

⇐ Day Count Convention - "30E/360 ISDA"

⇑ Day Count Convention - "30E/360 ISDA"

⇑⇑ Day Count Conventions