3. PLEAC Julia: Dates and Times¶

PLEAC = Language Examples Alike Cookbook by Guillaume Cottenceau et al. PLEAC examples were drawn from the "Perl Cookbook" by Tom Christiansen & Nathan Torkington, published by O'Reilly, and used with the publisher's permission. They provide a nice range of examples oriented toward data munging, the type of work I tend to want to do first when learning a new language.

The Julia examples below are principally translations from the Python version

Caution¶

I'm learning as I go, so the code below probably doesn't represent best practice. Your suggestions are welcome! Please file an issue or make a pull request to the github repo.

The examples are not complete. Missing items are generally noted in comments.

In [1]:

VERSION

Out[1]:

v"0.2.0-rc4"

In [2]:

using Datetime
n=now()

Out[2]:

2013-11-23T14:27:11 UTC

Pre-PLEAC: a brief look at Base time functions, Datetime.jl, and Calendar.jl¶

Julia includes a small set of c style time functions in its base modules. It addition there are the Calendar.jl and Datetime.jl packages. Many of the examples below use Datetime.jl. Examples related to epoch rely more on the Base time functions. Calendar.jl is also used in some cases; it is currently particularly strong at parsing and formatting (Calendar.jl is also good for internationalized formats, but those are not exercised in this notebook).

Base time functions¶

In [3]:

t=time()  #current time, unix epoch

Out[3]:

1.385216831873e9

In [4]:

dump(t)

Float64 1.385216831873e9

In [5]:

t2 = ccall(:clock_now, Float64, ())  #Seconds since unix epoch

Out[5]:

1.385216832207e9

In [6]:

t-t2

Out[6]:

-0.3340001106262207

TmStruct is ok per @karbacca (https://github.com/JuliaLang/julia/issues/4739)¶

time() is local (EDT in my case). Year field of 113 rather than 2013 reflects base of 1900.

Month field of 10 rather than 11 reflect zero-based month numbering.

In [7]:

tm=TmStruct(time())  #

Out[7]:

TmStruct(12,27,9,23,10,113,6,326,0,0,0,0,0,0)

In [8]:

tm2 = TmStruct(23,32,10,5,10,113,2,308,0)

Out[8]:

TmStruct(23,32,10,5,10,113,2,308,0,0,0,0,0,0)

In [9]:

strftime("%A",time())  #correct

Out[9]:

"Saturday"

In [10]:

help(TmStruct)

Loading help data...
Base.TmStruct([seconds])

   Convert a number of seconds since the epoch to broken-down format,
   with fields "sec", "min", "hour", "mday", "month",
   "year", "wday", "yday", and "isdst".

In [11]:

dump(tm)

TmStruct 
  sec: Int32 12
  min: Int32 27
  hour: Int32 9
  mday: Int32 23
  month: Int32 10
  year: Int32 113
  wday: Int32 6
  yday: Int32 326
  isdst: Int32 0
  _10: Int32 0
  _11: Int32 0
  _12: Int32 0
  _13: Int32 0
  _14: Int32 0

In [12]:

tns=time_ns() #high precision time

Out[12]:

0x0000e883391245e1

In [13]:

strftime(t)

Out[13]:

"11/23/2013 9:27:11 AM"

Apparent bug in strptime(), at least on Windows¶

The Window C lib doesn't appear to include strptime(), so maybe a Julia version? Python does this in /Lib/_strptime.py

In [14]:

methods(Base.strptime)

Out[14]:

# 2 methods for generic function "strptime":
strptime(timestr::Union(ASCIIString,UTF8String)) at libc.jl:48
strptime(fmt::Union(ASCIIString,UTF8String),timestr::Union(ASCIIString,UTF8String)) at libc.jl:50

In [15]:

Base.strptime("%Y/%m/%d","2013/11/4")

symbol could not be found strptime (-1): The specified procedure could not be found.

WARNING: backtraces on your platform are often misleading or partially incorrect

ccall: could not find function strptime
at In[15]:1
 in strptime at libc.jl:51

In [16]:

TmStruct(time())

Out[16]:

TmStruct(14,27,9,23,10,113,6,326,0,0,0,0,0,0)

In [17]:

help(ByteString)

Union(ASCIIString,UTF8String) is of type
DataType   : UnionType
  supertype: Type{T<:Top}
  fields   : (:types,)

In [18]:

isa("2013/11/4",ByteString)

Out[18]:

true

Datetime.jl¶

Datetime is a package created by @karbarcca. It can be installed via the package manager. You can find source code and documentation at: https://github.com/karbarcca/Datetime.jl.

In [19]:

Datetime.today()

Out[19]:

2013-11-23

In [20]:

Datetime.now()

Out[20]:

2013-11-23T14:27:14 UTC

In [21]:

Datetime.calendar(Datetime.today())

Out[21]:

ISOCalendar

In [22]:

Datetime.calendar(now())

Out[22]:

ISOCalendar

In [23]:

Datetime.timezone(now())

Out[23]:

Zone0

In [24]:

Datetime.offset(UTC)

Out[24]:

In [25]:

Datetime.today() + Datetime.days(4)

Out[25]:

2013-11-27

In [26]:

Datetime.today() - Datetime.weeks(1)

Out[26]:

2013-11-16

In [133]:

type cannot be constructed
at In[133]:1

Calendar.jl / ICU.jl¶

Calendar.jl builds on ICU.jl to provide an internationalized set of dates and times. It knows how to query the computer for local timezone settings and provides parsing and formatting options not currently available with Datetime.jl. It does require ICU binaries, so set-up can be a bit harder than Datetime.jl.

In [27]:

using ICU

In [28]:

ICU.getDefaultTimeZone()

Out[28]:

"America/New_York"

In [29]:

ICU.getNow() #epoch

Out[29]:

1.385216836751e12

In [30]:

ICU.ICUCalendar()

Out[30]:

ICUCalendar(Ptr{Void} @0x000000000319f1f0)

In [31]:

using Calendar

In [32]:

t0=Calendar.now()

Out[32]:

Nov 23, 2013, 9:27:17 AM EST

In [33]:

t = ymd_hms(2013, 3, 10, 1, 59, 59)

Out[33]:

Mar 10, 2013, 1:59:59 AM EST

In [34]:

typeof(t)

Out[34]:

CalendarTime (constructor with 1 method)

Warning: using Calendar.now in module Main conflicts with an existing identifier.

In [35]:

t + days(2)

Out[35]:

Mar 12, 2013, 2:59:59 AM EDT

In [36]:

delta =t0-t

Out[36]:

258 days + 7 hours + 27 minutes + 17.86600000038743 seconds

In [37]:

dump(delta)

FixedCalendarDuration 
  millis: Float64 2.2318037866e10

In [38]:

s = Calendar.format("yyyy-MMMM-dd EEE HH:mm:ss x", t)

Out[38]:

"2013-March-10 Sun 01:59:59 -05"

In [39]:

 t2 = Calendar.parse("yyyy-MMMM-dd EEE HH:mm:ss V", s)

Out[39]:

Mar 10, 2013, 1:59:59 AM EST

In [40]:

timezone(t2, "UTC")

Out[40]:

Mar 10, 2013, 6:59:59 AM GMT

Date to TmStruct¶

In [41]:

d = Datetime.today()

Out[41]:

2013-11-23

In [42]:

tmd = TmStruct(0,0,0,Datetime.day(d), Datetime.month(d)-1,Datetime.year(d)-1900,
               Datetime.dayofweek(d), Datetime.dayofyear(d),0)

Out[42]:

TmStruct(0,0,0,23,10,113,6,327,0,0,0,0,0,0)

In [43]:

#correct
strftime("Today is Day %w of the week (a %A). Day %d of the month (%B)",tmd)

Out[43]:

"Today is Day 6 of the week (a Saturday). Day 23 of the month (November)"

In [44]:

strftime("Day %j of the year(%Y), in week %W of the year.",tmd)

Out[44]:

"Day 328 of the year(2013), in week 47 of the year."

In [45]:

function Date2TmStruct(d::Datetime.Date)
    tmd = TmStruct(0,0,0,Datetime.day(d), Datetime.month(d)-1,Datetime.year(d)-1900,
                   Datetime.dayofweek(d),Datetime.dayofyear(d),0)
    return tmd
end

Out[45]:

Date2TmStruct (generic function with 1 method)

In [46]:

tmd=Date2TmStruct(d)

Out[46]:

TmStruct(0,0,0,23,10,113,6,327,0,0,0,0,0,0)

In [47]:

dd = date(tmd.year+1900,tmd.month+1,tmd.mday)

Out[47]:

2013-11-23

In [48]:

function TmStruct2Date(tmd::TmStruct)
     return Datetime.date(tmd.year+1900,tmd.month+1,tmd.mday)
end

Out[48]:

TmStruct2Date (generic function with 1 method)

In [49]:

TmStruct2Date(tmd)

Out[49]:

2013-11-23

In [50]:

import Base.strftime
function strftime(fmt::String, d::Datetime.Date)
  """strftime date formatting using Datetime.Date"""
  tmd = Date2TmStruct(d)
  return strftime(fmt, tmd)
end

Out[50]:

strftime (generic function with 4 methods)

In [52]:

strftime("%A",Datetime.today())

Out[52]:

"Saturday"

In [134]:

strftime("%Y-%m-%d", now())

Out[134]:

"2013-11-23"

Datetime to TmStruct¶

In [135]:

dt=now()

Out[135]:

2013-11-25T18:32:33 UTC

In [136]:

#Year field of 113 rather than 2013 reflects base of 1900.
#Month field of 10 rather than 11 reflect zero-based month numbering.
tm = TmStruct(23,32,10,5,10,113,2,308,0)
dump(tm)

TmStruct 
  sec: Int32 23
  min: Int32 32
  hour: Int32 10
  mday: Int32 5
  month: Int32 10
  year: Int32 113
  wday: Int32 2
  yday: Int32 308
  isdst: Int32 0
  _10: Int32 0
  _11: Int32 0
  _12: Int32 0
  _13: Int32 0
  _14: Int32 0

In [137]:

Datetime.second(dt), Datetime.minute(dt), Datetime.hour(dt), 
Datetime.day(dt), Datetime.month(dt), Datetime.year(dt), 
Datetime.dayofweek(dt), Datetime.dayofyear(dt)

Out[137]:

(33,32,18,25,11,2013,1,329)

? isdst should be 0 or 1. How do we get it from datetime? Maybe we can ignore it for formatting?

In [138]:

tmdt = TmStruct(Datetime.second(dt), Datetime.minute(dt), Datetime.hour(dt), 
                Datetime.day(dt), Datetime.month(dt)-1,Datetime.year(dt)-1900,
                Datetime.dayofweek(dt)-1,Datetime.dayofyear(dt),0)

Out[138]:

TmStruct(33,32,18,25,10,113,0,329,0,0,0,0,0,0)

In [206]:

?TmStruct

Base.TmStruct([seconds])

   Convert a number of seconds since the epoch to broken-down format,
   with fields "sec", "min", "hour", "mday", "month",
   "year", "wday", "yday", and "isdst".

In [195]:

function TmStruct2Datetime(tmd::TmStruct)
   return  datetime(int64(tmd.year+1900),int64(tmd.month+1),int64(tmd.mday), int64(tmd.hour), int64(tmd.min), int64(tmd.sec) )
end

Out[195]:

TmStruct2Datetime (generic function with 1 method)

In [202]:

tmd =TmStruct(time())

Out[202]:

TmStruct(17,49,13,25,10,113,1,328,0,0,0,0,0,0)

In [203]:

 TmStruct2Datetime(tm)

Out[203]:

2013-11-25T13:42:53 UTC

In [204]:

#strftime("%Y-%m-%d %h:%M:%s",time())
strftime("%Y %H:%M:%S",time())

Out[204]:

"2013 13:49:18"

In [57]:

function DateTime2TmStruct(d::Datetime.DateTime)
    tmdt = TmStruct(Datetime.second(dt), Datetime.minute(dt), Datetime.hour(dt), 
                Datetime.day(dt), Datetime.month(dt)-1,Datetime.year(dt)-1900,
                Datetime.dayofweek(dt),Datetime.dayofyear(dt),0)
    return tmdt
end

Out[57]:

DateTime2TmStruct (generic function with 1 method)

In [58]:

function strftime(fmt::String, dt::Datetime.DateTime)
  """strftime date formatting using Datetime.DateTime"""
  tmdt = DateTime2TmStruct(dt)
  return strftime(fmt, tmdt)
end

Out[58]:

strftime (generic function with 6 methods)

In [59]:

strftime("%A",dt)

Out[59]:

"Saturday"

PLEAC 3.0: Introduction¶

In [60]:

using Datetime

In [61]:

dayofyear(today())

Out[61]:

In [62]:

println("Today is day $(dayofyear(today())) of the current year.")

Today is day 327 of the current year.

In [63]:

println("Today is day $(dayofyear(today())) of $(year(today())).")

Today is day 327 of 2013.

PLEAC 3.1: Finding Today's Date¶

In [64]:

println("The date is $(today()).")

The date is Nov 23, 2013, 12:00:00 AM EST.

PLEAC 3.2: Converting DMYHMS to epoch seconds¶

In [65]:

now()

Out[65]:

2013-11-23T14:27:26 UTC

In [66]:

epoch_dt = datetime(1970,1,1,0,0,0)

Out[66]:

1970-01-01T00:00:00 UTC

In [67]:

now() - epoch_dt

Out[67]:

1385216871852

In [68]:

function datetime2unix(dt::DateTime)
    #returns difference in seconds, to match Base.time()
    #unix2datetime{T<:Offsets}(x::Int64,tz::Type{T}) = convert(DateTime{CALENDAR,tz},UNIXEPOCH + x + leaps(UNIXEPOCH + x))
    epoch_dt = datetime(1970,1,1,0,0,0)
    diff_secs = (dt - epoch_dt - Datetime.leaps(dt))/1000
    return  diff_secs 
end

Out[68]:

datetime2unix (generic function with 1 method)

In [69]:

dt=now()

Out[69]:

2013-11-23T14:27:27 UTC

In [70]:

ep=datetime2unix(dt)

Out[70]:

1.385216847391e9

In [71]:

(time() - datetime2unix(now())) #seconds difference

Out[71]:

0.0

In [72]:

(time() - datetime2unix(now(UTC))) 

Out[72]:

-0.003999948501586914

In [73]:

(time() - datetime2unix(now(EDT))) 

Out[73]:

-0.006000041961669922

In [74]:

println("Epoch seconds: $(time())")

Epoch seconds: 1.385216848683e9

PLEAC 3.3: Converting epoch seconds to DMYHMS¶

In [75]:

t= time()

Out[75]:

1.385216848954e9

In [76]:

#correct utc
unix2datetime( int64(t*1000) , UTC)

Out[76]:

2013-11-23T14:27:28 UTC

In [77]:

#correct local
unix2datetime( int64(t*1000) , EDT)

Out[77]:

2013-11-23T09:27:28 EST

In [78]:

function time2datetime(t::Float64, timezone)
  """time() style epoch to Datetime in specified timezone."""
  return unix2datetime( int64(t*1000) , timezone)  
end

time2datetime_utc(t::Float64) = time2datetime(t::Float64, UTC) 
time2datetime_est(t::Float64) = time2datetime(t::Float64, EDT) 

Out[78]:

time2datetime_est (generic function with 1 method)

In [79]:

# correct
time2datetime_est(t)

Out[79]:

2013-11-23T09:27:28 EST

PLEAC 3.4: Adding to or subtracting from a date¶

In [80]:

mydate = date(2013,1,2)

Out[80]:

2013-01-02

In [81]:

println("One day in the future is $(mydate + day(1))")

no method day(Int64,)
at In[81]:1

In [82]:

println("Two weeks in the past is $(mydate + week(-2))")

no method week(Int64,)
at In[82]:1

In [83]:

dt2 = date(2013,2,14)
dt2 - mydate

Out[83]:

In [84]:

birthtime = datetime(1973,1,18,3,45,50)

Out[84]:

1973-01-18T03:45:50 UTC

In [85]:

then = birthtime + seconds(5)+minutes(17)+hours(2)+days(55)

no method +(DateTime{ISOCalendar,Zone0},FixedCalendarDuration)
at In[85]:1
 in + at operators.jl:68

In [86]:

println("Then is $then")

then not defined
at In[86]:1

In [87]:

when = date(1973,1,18) + days(55)
println("Nat was 55 days old on $when")

no method +(Date{ISOCalendar},FixedCalendarDuration)
at In[87]:1

PLEAC 3.5: Difference of two dates¶

Using Datetime.jl¶

Date differences are given in days as a Day

In [88]:

diff = dt2 - mydate

Out[88]:

In [89]:

dump(diff)

Day{ISOCalendar} 43 days

Datetime differences are given in milliseconds as an Int64

In [90]:

dt1 = now()

Out[90]:

2013-11-23T14:27:44 UTC

In [91]:

dt2 = now()

Out[91]:

2013-11-23T14:27:44 UTC

In [92]:

diff_dt = dt2-dt1

Out[92]:

In [93]:

dump(diff_dt)

Int64 1

Something like partition_period(date, (date parts,)) partition_period(datetime,(datetime parts,)) might be handy¶

In [94]:

bree = datetime(1981,6,16,4,35,25)
nat =  datetime(1973,1,18,3,45,50)
dseconds =  (bree-nat)/1000
float_days = dseconds/(60*60*24)
ddays = int(float_days)  #convert from milliseconds to days

Out[94]:

In [95]:

println("There were $(int(ddays)) days between Nat and Bree")

There were 3071 days between Nat and Bree

In [96]:

dweeks = div(ddays,7)

Out[96]:

In [97]:

xdays = ddays % 7

Out[97]:

In [98]:

day_fraction = float_days - ddays

Out[98]:

0.03451388888879592

In [99]:

xhours = int(floor(24*day_fraction,0))

Out[99]:

In [100]:

dminutes = int(dseconds/60)

Out[100]:

In [101]:

day_seconds = dseconds-(ddays*24*60*60)

Out[101]:

2982.0

In [102]:

xhours= int(div(day_seconds, 60*60))

Out[102]:

In [103]:

xminutes = int(div(day_seconds, 60))

Out[103]:

In [104]:

xseconds = int(day_seconds % 60)

Out[104]:

In [105]:

#check the sum
xseconds + 60*xminutes + 60*60*xhours

Out[105]:

In [106]:

println("$weeks weeks, $xdays days, $xhours:$xminutes:$xseconds")

weeks weeks, 5 days, 0:49:42

using Calendar.jl¶

In [107]:

bree = ymd_hms(1981,6,16,4,35,25)
nat =  ymd_hms(1973,1,18,3,45,50)

Out[107]:

Jan 18, 1973, 3:45:50 AM EST

In [108]:

delta=bree-nat

Out[108]:

3070 days + 23 hours + 49 minutes + 35 seconds

delta is in milliseconds, just like Datetime.jl, so the rest is unchanged from above

In [109]:

dump(delta)

FixedCalendarDuration 
  millis: Float64 2.65333775e11

PLEAC 3.6: Day in a Week/Month/Year or Week Number¶

using Datetime.jl

In [110]:

when = Datetime.date(1981,6,16)

Out[110]:

1981-06-16

In [111]:

Datetime.dayofweek(when) # = Tuesday

Out[111]:

In [112]:

Datetime.year(when), Datetime.month(when), Datetime.day(when)

Out[112]:

(1981,6,16)

Formatted Datetime and Formatted Date

In [113]:

strftime("%A",Datetime.today())

Out[113]:

"Saturday"

In [114]:

strftime(when)

Out[114]:

"6/16/1981 12:00:00 AM"

In [115]:

#this is correct
strftime("Today is Day %w of the week (a %A). Day %d of the month (%B)",Datetime.today())

Out[115]:

"Today is Day 6 of the week (a Saturday). Day 23 of the month (November)"

In [116]:

strftime("1981-06-16 was Day %w of the week (a %A). Day %d of the month (%B)",when)

Out[116]:

"1981-06-16 was Day 2 of the week (a Tuesday). Day 16 of the month (June)"

In [117]:

strftime("Day %j of the year(%Y), in week %W of the year.",when)

Out[117]:

"Day 168 of the year(1981), in week 24 of the year."

PLEAC 3.7: Parsing Dates and Times from Strings¶

Datetime.jl parsing is a bit limited right now¶

In [118]:

# nope
datetime("Tue Jun 16 20:18:03 1981")

no method datetime(ASCIIString,)
at In[118]:2

Calendar.jl parsing is stronger¶

In [119]:

Calendar.parse("EEE MMM DD HH:mm:ss yyyy", "Tue Jun 16 20:18:03 1981")

Out[119]:

Jan 16, 1981, 8:18:03 PM EST

In [120]:

#time.strptime("16/6/1981", "%d/%m/%Y")
Calendar.parse("DD/M/yyyy","16/6/1981")

Out[120]:

Jan 16, 1981, 12:00:00 AM EST

PLEAC 3.8: Printing a Date¶

with Datetime.jl + new strftime()¶

In [121]:

dt=Datetime.now()
strftime("The date is %A (%a) %d/%m/%Y",dt) 

Out[121]:

"The date is Saturday (Sat) 23/11/2013"

Calendar.jl doesn't seem to know about string interpolation, so this is a bit clunkier.¶

In [122]:

cdt = Calendar.now()
Calendar.format("The date is yyyy",cdt)

Out[122]:

""

In [123]:

"""The date is $(Calendar.format(" EEEE (EEE) d/MM/yyyy",cdt))"""

Out[123]:

"The date is  Saturday (Sat) 23/11/2013"

In [124]:

Calendar.dayofweek(cdt)

Out[124]:

PLEAC 3.9: High-Resolution Timers¶

In [125]:

tic()

Out[125]:

0x0000e88a82c18c27

In [126]:

elapsed=toc()

elapsed time: 0.014813308 seconds

Out[126]:

0.014813308

In [127]:

# from https://github.com/JuliaLang/julia/issues/4478
function f1(n)
  sum = 0.0
  g1(k) = 1.0/k
  for i = 1:n
    sum += g1(i) 
  end
  sum
end

Out[127]:

f1 (generic function with 1 method)

In [128]:

f1(99)

Out[128]:

5.177377517639621

In [129]:

@time f1(1e6)

elapsed time: 0.128212042 seconds (48085868 bytes allocated)

Out[129]:

14.392726722864989

PLEAC 3.10: Short Sleeps¶

In [130]:

sleep(3.1) #sleep for 4 seconds

In [131]:

@time( sleep(3.1) )

elapsed time: 3.10030402 seconds (408 bytes allocated)

PLEAC 3.11: Program hopdelta¶

will not solve

In [132]:

;ipython nbconvert 3_pleac_datetime.ipynb

[NbConvertApp] Using existing profile dir: u'C:\\Users\\keithc\\.ipython\\profile_default'
[NbConvertApp] Converting notebook 3_pleac_datetime.ipynb to html
[NbConvertApp] Support files will be in 3_pleac_datetime_files\
[NbConvertApp] Loaded template html_full.tpl
[NbConvertApp] Writing 314208 bytes to 3_pleac_datetime.html