Why is my global variable not visible to my function?

Hello. I am trying to use a variable I define globally in a function that
follows within my script. Here is my code:

def currentYear = LocalDate.now().getYear()
def yearValue
def monthValue
def dayValue

boolean validateDate(String myYYYY, String myMM, String myDD) {

    // Acceptable range for years is assumed to be 120 years in the past to
40 years into the future

    log.error("in validateDate, myYYYY is ${myYYYY}")
    log.error("in validateDate, myMM is ${myMM}")
    log.error("in validateDate, myDD is ${myDD}")
    log.error("in validateDate, currentYear is 2023")
    log.error("in validateDate, currentYear is ${currentYear}")

    yearValue = Integer.parseInt(myYYYY)
    monthValue = Integer.parseInt(myMM.replaceFirst(/^0+/, ''))
    dayValue = Integer.parseInt(myDD.replaceFirst(/^0+/, ''))


    //if ((yearValue >= currentYear - 120 && yearValue <= currentYear + 40)
&& \
    //    (monthValue >= 1 && monthValue <= 12) && \
    //    (dayValue >= 1 && dayValue <= 31) \
    //   ) { return true }
    //   else { return false }

    //log.error("about to validate in validateDate, using
${yearValue.toString()} and ${currentYear.toString()}")
    log.error("about to validate in validateDate, using
${yearValue.toString()} and 2023")

    //if ((yearValue >= (currentYear - 120)) && (yearValue <= (currentYear
+ 40))) { return true } else { return false }
    if ((yearValue >= (2023 - 120)) && (yearValue <= (2023 + 40))) { return
true } else { return false }
}

In my log I find the first four log.error() output statements, but I do not
see the line that I expect:
in validateDate, currentYear is ${currentYear}

currentYear does not seem to be known to my function validateDate(). What
ios my error here? How can I correct this?

Thank you in advance for your help.