Why this expression places "NaN" in the output

Hi all… here is a serious newbie question for you all –

I have the following expression in a label:

Days since last visit:

I’m kind of wishing it would say something like 5 (if the number of days
between the two were five) …

for your info, “loaded date” is loaded into the form by means of case
management…

and also, when I make label fields to simply display the contents of those
two date fields, for debugging, they both display fine!

I’m sure it’s just a thing about how you work with date expressions… any
thoughts?

thanks
eric

Hi Eric,

For calculations with dates, you have to convert the stored value into a
date first. CommCare stores dates as strings that cannot be used for
calculations. So your expression would be:
int ( today() - date(/data/loaded_date) )

Best,
Devika

Field Manager, Dimagi
Skype: d_devika
+91 9555571141

··· On Wed, Jul 2, 2014 at 3:44 PM, Eric Stephan wrote:

Hi all… here is a serious newbie question for you all –

I have the following expression in a label:

Days since last visit:

I’m kind of wishing it would say something like 5 (if the number of days
between the two were five) …

for your info, “loaded date” is loaded into the form by means of case
management…

and also, when I make label fields to simply display the contents of those
two date fields, for debugging, they both display fine!

I’m sure it’s just a thing about how you work with date expressions…
any thoughts?

thanks
eric


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Aha… I knew it would be something like that. Big thanks for
your help. I will have to touch base with the reference
materials again. THANKS --Eric

··· On Wed, Jul 2, 2014, at 05:29 PM, Devika . wrote:

Hi Eric,

For calculations with dates, you have to convert the stored
value into a date first. CommCare stores dates as strings that
cannot be used for calculations. So your expression would be:
int ( today() - date(/data/loaded_date) )

Best,
Devika

Field Manager, Dimagi
Skype: d_devika
+91 9555571141

On Wed, Jul 2, 2014 at 3:44 PM, Eric Stephan <[1]estephan500@gmail.com> wrote:

Hi all… here is a serious newbie question for you all –

I have the following expression in a label:

Days since last visit:

I’m kind of wishing it would say something like 5 (if the
number of days between the two were five) …

for your info, “loaded date” is loaded into the form by means
of case management…

and also, when I make label fields to simply display the
contents of those two date fields, for debugging, they both
display fine!

I’m sure it’s just a thing about how you work with date
expressions… any thoughts?

thanks

eric

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