[#BloombergLP-bbldc-PeriodDayCountUtil-yearsDiff-0f]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bbldc.adoc[bbldc]::xref:BloombergLP/bbldc/PeriodDayCountUtil.adoc[PeriodDayCountUtil]::yearsDiff
:relfileprefix: ../../../
:mrdocs:

Return the (signed fractional) number of years between the specified `beginDate` and `endDate` according to the specified day‐count `convention` with periods starting on the specified `periodDate` values and each period having a duration of the specified `periodYearDiff` years (e.g., 0.25 for quarterly periods). If `beginDate <= endDate` then the result is non‐negative. The behavior is undefined unless `periodDate.size() >= 2`, the values contained in `periodDate` are unique and sorted from minimum to maximum, `min(beginDate, endDate) >= periodDate.front()`, `max(beginDate, endDate) <= periodDate.back()`, and `isSupported(convention)`. Note that reversing the order of `beginDate` and `endDate` negates the result; specifically, `|yearsDiff(b,e,pd,pyd,c) + yearsDiff(e,b,pd,pyd,c)| <= 1.0e‐15` for all dates `b` and `e`, periods `pd`, and year fraction per period `pyd`.

== Synopsis

Declared in `<bbldc_perioddaycountutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
static
double
yearsDiff(
    xref:BloombergLP/bdlt/Date.adoc[bdlt::Date] const& beginDate,
    xref:BloombergLP/bdlt/Date.adoc[bdlt::Date] const& endDate,
    xref:bsl/vector-00d.adoc[bsl::vector<bdlt::Date>] const& periodDate,
    double periodYearDiff,
    xref:BloombergLP/bbldc/DayCountConvention/Enum.adoc[DayCountConvention::Enum] convention);
----


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