Calculate difference in years, months, days if every month has 30 days

Question

Can't calculate difference between two dates in years, months, days. The problem is every month have 30 days, and every year have 365 days with no exceptions. There are a lot of topics here, but i haven't found any which can solve my problem or help with it. Every topic I found just solve problem calculating difference in normal way, which is simple. How can I calculate such difference?

I'm using Java 7 (there is no opportunity to install joda time) and groovy 2.4.0.

Examples are:

date from    date to       y  m  d
2014-02-01 - 2015-02-01 => 1  0  1
2000-02-10 - 2003-01-18 => 2  11 9
2004-02-02 - 2004-06-24 => 0  4  23

Thanks.

Answer 1

Came up with this in Groovy, not sure if it fits your requirements, but it gives the results in the question:

def dateMalarkey(Date from, Date to) {
    def val = [from, to].collect { d ->
        def cal = Calendar.instance
        cal.time = d
        [y: cal[Calendar.YEAR], m: cal[Calendar.MONTH], d: cal[Calendar.DAY_OF_MONTH]]
    }.inject { p, n ->
        [y: Math.abs(p.y - n.y), m: Math.abs(p.m - n.m), d: Math.abs(p.d - n.d)  + 1]
    }
    val.days = val.y * 365 + val.m * 30 + val.d
    val
}

def inputs = [
    [from: '2014-02-01', to: '2015-02-01'],
    [from: '2000-02-10', to: '2003-01-18'],
    [from: '2004-02-02', to: '2004-06-24']
]

inputs.each { d ->
    println "$d.from - $d.to => " +
        dateMalarkey(Date.parse('yyyy-MM-dd', d.from), Date.parse('yyyy-MM-dd', d.to))
}