Dynamic increase starting at t=0 crashes

contract$addDynamics(t=0, SumInsuredDelta = 2000)

Fehler in `+.Date`(left, right) : 
 binary + is not defined for "Date" objects 
11. stop("binary + is not defined for \"Date\" objects") 
10. `+.Date`(left, right) 
9.  eval(f) 
8.  eval(f) 
7.  Ops.data.frame(arr1, arr2) at InsuranceContract.R#688
6.  sumPaddedArrays(arr1 = vals, arr2 = b$Values[[field]], pad2 = b$Parameters$ContractData$blockStart) at InsuranceContract.R#697
5.  consolidateField("reservesBalanceSheet") at InsuranceContract.R#724
4.  self$consolidateBlocks(valuesFrom = t) at InsuranceContract.R#397
3.  (function (id = NULL, block = NULL, t = block$Values$int$blockStart,  [...]
2.  do.call(self$addBlock, params) at InsuranceContract.R#484
1.  L1X.Bsp$addDynamics(t = 0, SumInsuredDelta = 2000)