Rekenen met datum en tijd

Aangezien \(t=0\) overeenkomt met 1 januari, komt \(t=347\) overeen met \(348\text{ }\text{januari}\text{.}\)

\(348\text{ }\text{januari}\)
\(\text{ }=348-31\text{ (januari)}=317\text{ }\text{februari}\)
\(\text{ }=317-28\text{ (februari)}=289\text{ }\text{maart}\)
\(\text{ }=289-31\text{ (maart)}=258\text{ }\text{april}\)
\(\text{ }=258-30\text{ (april)}=228\text{ }\text{mei}\)
\(\text{ }=228-31\text{ (mei)}=197\text{ }\text{juni}\)
\(\text{ }=197-30\text{ (juni)}=167\text{ }\text{juli}\)
\(\text{ }=167-31\text{ (juli)}=136\text{ }\text{augustus}\)
\(\text{ }=136-31\text{ (augustus)}=105\text{ }\text{september}\)
\(\text{ }=105-30\text{ (september)}=75\text{ }\text{oktober}\)
\(\text{ }=75-31\text{ (oktober)}=44\text{ }\text{november}\)
\(\text{ }=44-30\text{ (november)}=14\text{ }\text{december}\)

Aangezien \(t=0\) overeenkomt met 29 juli 2017, komt \(t=92\) overeen met \(29+92=121\text{ }\text{juli}\text{.}\)

\(121\text{ }\text{juli}\)
\(\text{ }=121-31\text{ (juli)}=90\text{ }\text{augustus}\)
\(\text{ }=90-31\text{ (augustus)}=59\text{ }\text{september}\)
\(\text{ }=59-30\text{ (september)}=29\text{ }\text{oktober}\)
Dus bij \(t=92\) hoort 29 oktober 2017.

16 maart 2017 is \(t=0\)
31 maart 2017 is \(t=31-16=15\)
30 april 2017 is \(t=15+30=45\)
31 mei 2017 is \(t=45+31=76\)
30 juni 2017 is \(t=76+30=106\)
7 juli 2017 is \(t=106+7=113\)

\(t=16{,}9\) valt dan in \(\text{2020}+16=\text{2036}\text{.}\)

\(\text{2014}\) komt dan overeen met \(t=\text{2014}-\text{1990}=24\text{.}\)

De maand september heeft \(30\) dagen.

De \(10\)e maand van het kalenderjaar is \(\text{oktober}\text{.}\)

Op \(t=4{,}054\) is het \(4\text{ }\text{uur}\) en \(0{,}054⋅60=3{,}24\text{ }\text{minuten}\) later dan \(\text{5:00}\text{ }\text{uur}\text{.}\)
Het is dan dus \(\text{9:03}\text{ }\text{uur}\text{.}\)

Om \(\text{16:02}\text{ }\text{uur}\) is het \(10\text{ }\text{uur}\) en \(2\text{ }\text{minuten}\) later dan \(\text{6:00}\text{ }\text{uur}\text{.}\)
Dat is dus bij \(t=10+{2 \over 60}=10{,}03333...\text{.}\)

\(18{,}3\text{ }\text{dagen}=18{,}3⋅24\text{ }\text{uren}=439{,}2\text{ }\text{uren}\)

\(1\,032\text{ }\text{seconden}=1\,032:60\text{ }\text{minuten}=17{,}2\text{ }\text{minuten}\)

\(0{,}25\text{ }\text{uren}=0{,}25⋅60=15\text{ }\text{minuten}\text{,}\) dus \(6{,}25\text{ }\text{uren}=6\text{ }\text{uren}\) en \(15\text{ }\text{minuten}\text{.}\)

\(3\text{ }\text{jaar}\) en \(2\text{ }\text{maanden}=3+{2 \over 12}=3{,}166...\text{ }\text{jaar}\text{.}\)

\(4\text{ }\text{dagen}=4⋅24⋅3\,600=345\,600\text{ }\text{seconden}\)
\(3\text{ }\text{uren}=3⋅3\,600=10\,800\text{ }\text{seconden}\)
\(39\text{ }\text{minuten}=39⋅60=2\,340\text{ }\text{seconden}\)
Dus \(345\,600+10\,800+2\,340+5=358\,745\text{ }\text{seconden}\)

\(417\,380\text{ }\text{seconden}={417\,380 \over 24⋅60⋅60}=4{,}830...\text{ }\text{dagen}\)
\(0{,}830...\text{ }\text{dagen}=0{,}830...⋅24=19{,}938...\text{ }\text{uren}\)
\(0{,}938...\text{ }\text{uren}=0{,}938...⋅60=56{,}333...\text{ }\text{minuten}\)
\(0{,}333...\text{ }\text{minuten}=0{,}333...⋅60=20\text{ }\text{seconden}\)
Dus \(4\text{ }\text{dagen}\text{,}\) \(19\text{ }\text{uren}\text{,}\) \(56\text{ }\text{minuten}\) en \(20\text{ }\text{seconden}\text{.}\)

\(1\text{ }\text{etmaal}=24\text{ }\text{uren}\)