Hour/minute adds one hour from datetime with lubridate

Question

I would like to extract the hour/minute/second from a datetime. Example dataframe:

df <- structure(list(Study_date_time_PACS = structure(c(1515146548, 1515146548, 1514970658, 1514970658, 1515151732, 1515151732, 1517476589, 1517476589, 1543848246, 1543848246),
                                                class = c("POSIXct", "POSIXt"), 
                                                tzone = "UTC")),
          .Names = "Study_date_time", 
          row.names = c(NA, -10L), 
          class = c("tbl_df", "tbl", "data.frame"))
print(df)


# A tibble: 10 x 1
   Study_date_time    
   <dttm>             
 1 2018-01-05 10:02:28
 2 2018-01-05 10:02:28
 3 2018-01-03 09:10:58
 4 2018-01-03 09:10:58
 5 2018-01-05 11:28:52
 6 2018-01-05 11:28:52
 7 2018-02-01 09:16:29
 8 2018-02-01 09:16:29
 9 2018-12-03 14:44:06
10 2018-12-03 14:44:06

So I run this code but it adds one hour to the "hour"? How can I fix this. I assume it must be something with summertime...

library(lubridate)
df %>% 
  mutate(hour_min = hms::as.hms(Study_date_time))

# A tibble: 10 x 2
   Study_date_time     hour_min
   <dttm>              <time>  
 1 2018-01-05 10:02:28 11:02   
 2 2018-01-05 10:02:28 11:02   
 3 2018-01-03 09:10:58 10:10   
 4 2018-01-03 09:10:58 10:10   
 5 2018-01-05 11:28:52 12:28   
 6 2018-01-05 11:28:52 12:28   
 7 2018-02-01 09:16:29 10:16   
 8 2018-02-01 09:16:29 10:16   
 9 2018-12-03 14:44:06 15:44   
10 2018-12-03 14:44:06 15:44

score 1 · Accepted Answer · answered Feb 15 '19 at 14:52

Probaby due to the timezone-element that gets stripped... Let me guess: You live in a UTC+0100 - region of the planet?

You can use the force_tz() function from the lubridate-package.. but be careful!! Timezones are always a b#tch to work with, so handle with care!

df %>% mutate(hour_min = hms::as.hms( force_tz( Study_date_time ) ) )

# # A tibble: 10 x 2
#   Study_date_time     hour_min
#   <dttm>              <time>  
# 1 2018-01-05 10:02:28 10:02   
# 2 2018-01-05 10:02:28 10:02   
# 3 2018-01-03 09:10:58 09:10   
# 4 2018-01-03 09:10:58 09:10   
# 5 2018-01-05 11:28:52 11:28   
# 6 2018-01-05 11:28:52 11:28   
# 7 2018-02-01 09:16:29 09:16   
# 8 2018-02-01 09:16:29 09:16   
# 9 2018-12-03 14:44:06 14:44   
# 10 2018-12-03 14:44:06 14:44

@ Wimpel: I have asked a new question [link](https://stackoverflow.com/questions/54744899/time-zone-gets-lost-with-lubridate-when-creating-a-new-datetime-component-from-i) — xhr489, Feb 18 '19 at 10:16

arg0naut91 · Answer 2 · 2019-02-15T15:06:06.677

0

I agree that this likely a tz issue (perhaps you can just do hms::as.hms(Study_date_time, tz = 'UTC')) and it'll disappear), however I think you'd also do good without any package, e.g.:

df %>% 
  mutate(hour_min = format(Study_date_time, "%H:%M"))

edited Feb 15 '19 at 15:06

answered Feb 15 '19 at 14:55

arg0naut91

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@ arg0naut: Thanks! I don't think format will work. I need the hour/minute to make a filter with time on Fridays between 8 and 14:30. I will get back latter, maybe on monday, I don't have a computer now. – xhr489 Feb 15 '19 at 18:17
1

@ arg0naut, well I have used ``tz`` option on my date. But it does not get carried over to a new variable created with lubridate. – xhr489 Feb 18 '19 at 09:51
@ arg0naut: I have asked a new question [link](https://stackoverflow.com/questions/54744899/time-zone-gets-lost-with-lubridate-when-creating-a-new-datetime-component-from-i) – xhr489 Feb 18 '19 at 10:18

Hour/minute adds one hour from datetime with lubridate

2 Answers2