I am in the process of optimizing some UniVerse data access code we have which uses UniObjects. After some experimentation, it seems that using a UniSession.OConv call to parse certain things such as decimal numbers (most we have a MR4 or MR2 or MR2$) and dates (almost all are D2/) is extremely slow (I think it might make a call back to the server to parse it).
I have already built a parser for the MR*[$] codes, but I was wondering about the dates as they are stored so I can build one for D2/. Usually they seem to be stored as a 5 digit number. I thought it could be number of days since the Unix Epoch since our UniVerse server runs on HP-UX, but after finding '15766' as a last modified date and multiplying it by 86400 (seconds per day), I got March 02, 2013 which doesn't make sense as a last modified date since as far as I know that is still in the future.
Does anyone know what the time base of these date numbers are?
It is stored as a number of days. Just do a conversion on 0 and you will get the start date.
Edit:
As noted by Los, the Epoch used in UniVerse (and UniData) is 31st Dec 1967.
In Universe and any other Pick database, Dates and Times are stored as separate values.
The internal date is the number of days before of after 31/12/1967, which is day zero.
The internal time is the number of seconds after midnight. It can be stored as a decimal but is not normally.
In TCL there is a CDT command (stands for Convert Date) that converts dates from human readable to numeric and and vice versa:
CDT 9/28/2017
* Result: 18169
CDT 18169
* Result: 09/28/2017
Related
I'm interested in knowing the different possibilities to operate with datetimes in SQLite and understand its pros and cons. I did not find anywhere a detailed explanation of all the alternatives.
So far I have learned that
SQLite doesn't actually have a native storage class for timestamps /
dates. It stores these values as NUMERIC or TEXT typed values
depending on input format. Date manipulation is done using the builtin
date/time functions, which know how to convert inputs from the other
formats.
(quoted from here)
When any operation between datetimes is needed, I have seen two different approaches:
julianday function
SELECT julianday(OneDatetime) - julianday(AnotherDatetime) FROM MyTable;
Number of days is returned, but this can be fractional.
Therefore, you can also get some other measures of time with some extra operations. For instance, to get minutes:
SELECT CAST ((
julianday(OneDatetime) - julianday(AnotherDatetime)
) * 24 * 60 AS INTEGER)
Apparently julianday could cause some problems:
Bear in mind that julianday returns the (fractional) number of 'days'
- i.e. 24hour periods, since noon UTC on the origin date. That's usually not what you need, unless you happen to live 12 hours west of
Greenwich. E.g. if you live in London, this morning is on the same
julianday as yesterday afternoon.
More information in this post.
strftime function
SELECT strftime("%s", OneDatetime)-strftime("%s", AnotherDatetime) FROM MyTable;
Number of seconds is returned. Similarly, you can also get some other measures of time with some extra operations. For instance, to get minutes:
SELECT (strftime("%s", OneDatetime)-strftime("%s", AnotherDatetime))/60 FROM MyTable;
More information here.
My conclusion so far is: julianday seems easier to use, but can cause some problems. strftime seems more verbose, but also safer. Both of them provide only as results a single unit (either days or hours or minutes or seconds), but not a combination of many.
Question
1) Is there any other possibility to operate with datetimes?
2) What would be the best way to get directly the difference of two datetimes in time format (or date or datetime), where datetime would be formatted as 'YYYY-mm-dd HH:MM:SS', and the result would be something in the same format?
I would have imagined that something like the following would work, but it does not:
SELECT DATETIME('2016-11-04 08:05:00') - DATETIME('2016-11-04 07:00:00') FROM MyTable;
> 01:05:00
Julian day numbers are perfectly safe when computing differences.
The only problem would be if you tried to convert them into a date by truncating any fractional digits; this would result in noon, not midnight. (The same could happen if you tried to store them in integer variables.) But that is not what you're doing here.
SQLite has no built-in function to compute date/time differences; you have to convert date/time values into some number first. Whether you use (Julian) days or seconds does not really matter from a technical point of view; use whatever is easier in your program.
If you started with a different format, you might want to convert the resulting difference back into that format, e.g.:
time(difference_value, 'unixepoch') -- from seconds to hh:mm:ss
time(0.5 + difference_value) -- from Julian days to hh:mm:ss
I have to convert IST(India) to EET(Finland) timing using perl or shell ...
Means i have to subtract 3 hours,30 minutes from a given specific (ISD)time (not from the current time).
Time is in this format: YYYY-MM-DD HH:MM:SS
For ex: IST: 2016-01-01 02:30:00
Then after subtracting 3hours and 30 minutes ,I should get,
EET: 2015-12-31 23:00:00
The thing is after subtracting,if required the date,month and year should also change.
Can i do this using perl? Can anyone help me on this?
I'm not going to give you the actual code as you haven't demonstrated that you have made any effort to solve this yourself.
But the way to do this is to use a real Date/Time handling library. In Perl, that probably means DateTime. You can use DateTime::Format::Strptime to generate a DateTime object from a string.
In summary, your approach should be:
Parse your string into a DateTime object (being careful to ensure that the parsing object knows that the time zone is ISD (Icelandic time, I assume [Update: or, more likely, Indian]).
Convert the time zone in your parsed object to EET.
Use the parsed object's strftime method to produce the output time in the correct output.
Update: And I'll just add the standard advice about handling dates and times. You should always transmit and store dates and times in UTC. Local time zones should only every be displayed to users.
How do I get date function to return date according to current system date?
Right now, with the code snippet below, it always returns UK time, not the current system date.
<calculate>
<script>$ = concat( num2date(date(), DateFmt()), " ", num2Time(Time(), TimeFmt()) )</script>
Any help is appreciated!
It's probably not UK time exactly, but rather GMT (or UTC, to use a more precise term). The UK happens to be aligned to GMT in the winter, but in the summer it advances one hour to BST for daylight saving time.
Now, I've never used LiveCycle myself, but nonetheless, I've read through the somewhat minimal docs for LiveCycle FormCalc Date and Time Functions, and the spec, and it appears to me that a few critical mistakes were made.
The date and time functions return UTC-based values, but only the time-related functions have been made aware of the local time zone. That is, there are separate Num2Time and Num2GMTime functions, but there is only one Num2Date function.
The Num2Date function works in terms of whole integer days, and thus they are simply days since 1900-01-01. Therefore, the number being passed in to the function must already be representative of the desired time zone. However, the Date function only gets the current GMT date. There does not appear to be a function to get the current local date.
It's different on the time side, because of the millisecond precision involved. However, there's yet another flaw here. Despite the docs saying that the Time function returning "the number of milliseconds since the epoch", its actually returning only the number of milliseconds since midnight GMT. There is no day-over-day accumulation of milliseconds from the date part. The docs here are even lying in their sample code which says:
Returns the current system time as the number of milliseconds since the epoch.
Time() => 71533235 at precisely 3:52:15 P.M. on September 15th, 2003 to a user in the Eastern Standard Time (EST) zone.
If that was indeed the case (and ensuring to use their 1900-01-01 epoch), the value would actually include an additional 3272572800000 milliseconds representing the days between 1900-01-01 and 2003-09-15, bringing the total timestamp to 3272644333235. Additionally, there's a typo there, because the timestamp they give is 3:52:13, not 3:52:15. Clearly nobody paid close attention to these docs!
The real problem is that one cannot be certain that the number of milliseconds since midnight of the current day in the local time zone is the same on every day. If instead of getting the current time, you were working with past stored time values, you might be an hour off (+ or -) if the current offset is different due to daylight saving time. Example: Eastern time might be UTC-5 or UTC-4, but only the offset currently in effect will be used by the Num2Time function, even if the date you're working with is using the other offset.
So, in summary, the Date function is insufficient, leading to your observations, and the date/time functionality in general is poorly designed. Given the constraints of this API, I can't even recommend a workaround. There would have to be a LocalDate function of some kind to be used instead of the Date function, but it doesn't exist.
The only advice I can offer is that it appears (from my research, not experience) that LiveCycle can use either FormCalc or JavaScript. So - use JavaScript instead.
I've discovered an issue with some of data being stored in MongoDB. We have a field that stores a Date, and normally this includes values like ISODate("1992-08-30T00:00:00.000Z") or ISODate("1963-08-15T00:00:00.000Z"). That's nice and straight-forward; I can easily look at those dates and see August 30, 1992 or August 15, 1963.
However, I've noticed a couple of entries where the date looks something like this instead:
Date(-61712668800000)
I'm honestly not sure how the data got persisted that way in the first place, as it should have been stored the former way. And I'll have to address the software bug with my code that is intermittently causing it to be stored that way.
However, the bigger problem is what to do with data entries that look like that. I'm not even sure what date that was supposed to be. My first assumption is that it's just milliseconds, like a UNIX timestamp or something, but that's not right. Even if I flip the negative sign and remove some of the trailing zeros, that still ends up being a date way in the future (e.g. July 23, 2165), and that's not correct. It should be a date in the past.
And the other big problem is that I'm not sure how to even search for this in the database. I can't utilize a $type query because the type is still 9 (i.e. it still thinks it's a "Date").
Has anyone else encountered these weird date entries before? How can I find them? And how can I recover the actual date from them?
The problem seems to be that your code is storing dates prior to the epoch, which are furthermore so far into the past that they cannot be represented using an ISODate wrapper:
As per the documentation
(emphasis added)
Date
BSON Date is a 64-bit integer that represents the number of
milliseconds since the Unix epoch (Jan 1, 1970). This results in a
representable date range of about 290 million years into the past and
future.
The official BSON specification refers to the BSON Date type as the
UTC datetime.
Changed in version 2.0: BSON Date type is signed. [2] Negative values
represent dates before 1970.
Although not explicitly stated in the Mongo documentation, it appears that they are following a strict interpretation of the ISO 8601 standard and not one of the variants which are allowed "by trading partner agreement" based on what I found at wikipedia
Years
YYYY ±YYYYY ISO 8601 prescribes, as a minimum, a
four-digit year [YYYY] to avoid the year 2000 problem. It therefore
represents years from 0000 to 9999, year 0000 being equal to 1 BC and
all others AD. However, years prior to 1583 are not automatically
allowed by the standard. Instead "values in the range [0000] through
[1582] shall only be used by mutual agreement of the partners in
information interchange."[9]
To represent years before 0000 or after 9999, the standard also
permits the expansion of the year representation but only by prior
agreement between the sender and the receiver.[10] An expanded year
representation [±YYYYY] must have an agreed-upon number of extra year
digits beyond the four-digit minimum, and it must be prefixed with a +
or − sign[11] instead of the more common AD or BC (or the less widely
used BCE/CE) notation; by convention 1 BC is labelled +0000, 2 BC is
labeled -0001, and so on.[12]
If you read through the rest of the article you will also see that the reason the number of digits must be pre-defined is so that the date can be stored unambiguously without using separator characters such as "-" between the components.
I am developing a plugin written in Lua, and I need a way to calculate Unix time or at least a way to compare 2 date strings.
The function I can use only returns date string in the following format
"1/17/2014 6:50 PM"
Is there a way to convert this string to a Unix time?
Unfortunately I don't have access to the OS library so things like os.time() do not work.
Is there any library or something similar that I can work with?
I also thought about splitting the string into parts, but I need a way to add/subtract time
Just compare normalized timestamps:
function normalize(a)
local m,d,y,h,mi,n=a:match("(%d+)/(%d+)/(%d+)%s+(%d+):(%d+)%s+(%w+)")
if n=="PM" then h=h+12 end
return string.format("%04d%02d%02d%02d%02d",y,m,d,h,mi)
end
Date arithmetic is another story. For a complete, pure Lua date library, see luatz or https://github.com/Tieske/date.
If you need to only compare two time, you don't need to get each time's Unix timestamp. One possible solution is to get the time fields from the string like this:
local time = "1/17/2014 6:50 PM"
local month, day, year, hour, minute, am_pm = time:match("(%d+)/(%d+)/(%d+)%s+(%d+):(%d+)%s+(%w+)")
print(month, day, year, hour, minute, am_pm)
Output: 1 17 2014 6 50 PM
Then compare two time from comparing their year, if they are equal, then month, and so on. Remember to use tonumber to compare them by number, not the string itself.