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How to convert long number to date in actual local format?

Greeting
Jakub

On 20/09/2021 15.26, Jakub wrote:
> Welcome
>
> How to convert long number to date in actual local format?

What is "long number"? Can you give examples?

--
Cheers,
Carlos E.R.

"Carlos E. R." <robin_listas@es.invalid> wrote

| > How to convert long number to date in actual local format?
| | What is "long number"? Can you give examples?
| I wondered about that, too. I think there used to be
a system for determining time as a 4-byte integer that
indicated seconds since sometime in 1970. But we're
running out of storage if it's a signed integer. And looking
it up in the Win32 API, I can't find a function to conver
to/from such a number. A function could be written,
but who would be using such numeric dates in the first
place?

On 20/09/2021 16.12, Mayayana wrote:
> "Carlos E. R." <robin_listas@es.invalid> wrote
>
> | > How to convert long number to date in actual local format?
> |
> | What is "long number"? Can you give examples?
> |
> I wondered about that, too. I think there used to be
> a system for determining time as a 4-byte integer that
> indicated seconds since sometime in 1970. But we're
> running out of storage if it's a signed integer. And looking
> it up in the Win32 API, I can't find a function to conver
> to/from such a number. A function could be written,
> but who would be using such numeric dates in the first
> place?

I have seen conversion functions in the free pascal library, for
instance. Surely also C, but I have not looked in many years.

Yes, there are several implementations. You can assign a number of bytes
for each element in the date-time. Or you can count number of "ticks"
since a certain moment; ticks could be timer interrupts in an MsDOS PC,
or seconds since "the epoch" as does Linux (or Unix).

For example, Linux has user tools to do the conversion:

cer@minas-tirith:~> date +%s
1632148500
cer@minas-tirith:~> date -d @1632148500 +"%F %T %z"
2021-09-20 16:35:00 +0200
cer@minas-tirith:~>

I have not heard of anything in Android. Probably in code, but I do not
code for Android. In any case, we have to know what "long number" means.

--
Cheers,
Carlos E.R.

Mayayana <mayayana@invalid.nospam> wrote:
> "Carlos E. R." <robin_listas@es.invalid> wrote
>
>| > How to convert long number to date in actual local format?
>|
>| What is "long number"? Can you give examples?
>|
> I wondered about that, too. I think there used to be
> a system for determining time as a 4-byte integer that
> indicated seconds since sometime in 1970. But we're
> running out of storage if it's a signed integer. And looking
> it up in the Win32 API, I can't find a function to conver
> to/from such a number. A function could be written,
> but who would be using such numeric dates in the first
> place?

Who would be interested in the Win32 API when programming for android?

This representation of a date+time is very convenient when you need
to perform arithmetic on it. E.g. "1 day later", "1 week before",
"how many days between these dates", etc.

It is also convenient internally to the computer, as incrementing it
is merely incrementing an integer value. No need to check for those
complex rules that are involved in times and dates.

It will work until early 2038, when a problem similar to Y2K will occur.

Am 20.09.21 um 16:12 schrieb Mayayana:
> "Carlos E. R." <robin_listas@es.invalid> wrote
>
> | > How to convert long number to date in actual local format?
> |
> | What is "long number"? Can you give examples?
> |
> I wondered about that, too. I think there used to be

Me too.

--
De gustibus non est disputandum

On 20/09/2021 16.41, Rob wrote:
> Mayayana <mayayana@invalid.nospam> wrote:
>> "Carlos E. R." <robin_listas@es.invalid> wrote
>>
>> | > How to convert long number to date in actual local format?
>> |
>> | What is "long number"? Can you give examples?
>> |
>> I wondered about that, too. I think there used to be
>> a system for determining time as a 4-byte integer that
>> indicated seconds since sometime in 1970. But we're
>> running out of storage if it's a signed integer. And looking
>> it up in the Win32 API, I can't find a function to conver
>> to/from such a number. A function could be written,
>> but who would be using such numeric dates in the first
>> place?
>
> Who would be interested in the Win32 API when programming for android?
>
> This representation of a date+time is very convenient when you need
> to perform arithmetic on it. E.g. "1 day later", "1 week before",
> "how many days between these dates", etc.
>
> It is also convenient internally to the computer, as incrementing it
> is merely incrementing an integer value. No need to check for those
> complex rules that are involved in times and dates.
>
> It will work until early 2038, when a problem similar to Y2K will occur.
>

You are asuming a particular representation of dates + times in a long
number. We don't know if this is what the OP means.

--
Cheers,
Carlos E.R.

"Carlos E. R." <robin_listas@es.invalid> wrote

| > It will work until early 2038, when a problem similar to Y2K will occur.
| >
| | You are asuming a particular representation of dates + times in a long
| number. We don't know if this is what the OP means.
|

The OP also didn't mention the language. I expect most
languages have plenty of functions for comparing dates
without converting them to numeric. Javascript, for example,
has a Date object.

Mayayana <mayayana@invalid.nospam> wrote:
> "Carlos E. R." <robin_listas@es.invalid> wrote
>
>| > It will work until early 2038, when a problem similar to Y2K will occur.
>| >
>|
>| You are asuming a particular representation of dates + times in a long
>| number. We don't know if this is what the OP means.
>|
>
> The OP also didn't mention the language. I expect most
> languages have plenty of functions for comparing dates
> without converting them to numeric. Javascript, for example,
> has a Date object.

As it is so hard to compare two dates as strings (especially in American
notation!), those functions internally often convert them to a long
number and then compare those numbers.

Mayayana wrote:

> I think there used to be
> a system for determining time as a 4-byte integer that
> indicated seconds since sometime in 1970. But we're
> running out of storage if it's a signed integer. And looking
> it up in the Win32 API, I can't find a function to conver
> to/from such a number. A function could be written,
> but who would be using such numeric dates in the first
> place?

Mayayana should be surprised. 😲

Here is where numeric dates are used:
* Windows: Windows NTFS FILETIME is a numeric datetime.
(The number of 100-nanosecond intervals since 1 Jan 1601 UTC.)
* Linux, Unix: Unix time is a numeric datetime.
(The number of seconds since 1 Jan 1970 00:00:00 UTC.)
* Java: (The number of milliseconds since 1 Jan 1970 00:00:00 UTC.)

There already are functions to do the conversion.

The *Win32* API might appear irrelevant for a question in the *Android*
newsgroup. Even so, let me direct Mayayana to this Microsoft web page:
<https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/localtime-localtime32-localtime64>

Mayayana could observe that the 64-bit versions will not be running out
of storage for a very long time.

..

"Antonio Bodoni" <antoniobodoni@invalid.nospam> wrote

|
| Mayayana should be surprised. 😲
| | Here is where numeric dates are used:
| * Windows: Windows NTFS FILETIME is a numeric datetime.
| (The number of 100-nanosecond intervals since 1 Jan 1601 UTC.)
| * Linux, Unix: Unix time is a numeric datetime.
| (The number of seconds since 1 Jan 1970 00:00:00 UTC.)
| * Java: (The number of milliseconds since 1 Jan 1970 00:00:00 UTC.)
| | There already are functions to do the conversion.
|

I see. Like FileTimeToSystemTime. Thanks. Though no one
is actually dealing with the numbers directly. I guess we
may never know what Jakub is trying to do.

"Carlos E. R." <robin_listas@es.invalid> wrote in news:vngm1ixlb7.ln2
@minas-tirith.valinor:

> On 20/09/2021 15.26, Jakub wrote:
>> Welcome
>>
>> How to convert long number to date in actual local format?
>
> What is "long number"? Can you give examples?
>
>

I presume the OP means spreadsheet numbering system. While I have a
lot of experience with date and time using Excel, I'm not about to
try to guess what Jakub actually wants. The internet will usually
find an answer such questions.

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