title: How to merge date and time into 1 object
body: <p>My data is this:</p>
  
  <pre><code>structure(list(Date = structure(c(1509408000, 1509408000, 1509408000, 
  1509408000, 1509408000, 1509408000), class = c("POSIXct", "POSIXt"
  ), tzone = "UTC"), Time = structure(c(-2208988860, -2208988920, 
  -2208988980, -2208989040, -2208989100, -2208989160), class = c("POSIXct", 
  "POSIXt"), tzone = "UTC"), O = c(54.62, 54.62, 54.62, 54.62, 
  54.63, 54.63), H = c(54.63, 54.63, 54.62, 54.62, 54.63, 54.63
  ), L = c(54.62, 54.62, 54.62, 54.62, 54.62, 54.62), C = c(54.62, 
  54.62, 54.62, 54.62, 54.62, 54.62), date.time = structure(c(NA_real_, 
  NA_real_, NA_real_, NA_real_, NA_real_, NA_real_), class = c("POSIXct", 
  "POSIXt"), tzone = "")), row.names = c(NA, -6L), class = c("tbl_df", 
  "tbl", "data.frame"))
  </code></pre>
  
  <p>I want the time to either have the same date as in the Date column or have no date at all. 
  For the first solution, I have tried to take the date from Date column and the time from the Time column to create a datetime column.</p>
  
  <p>I have tried the following code: </p>
  
  <pre><code>data_frame2$date.time &lt;- as.POSIXct(paste0(data_frame2$Date,  data_frame2$Time), format="%Y-%m-%d %H:%M:%S")
  </code></pre>
  
  <p>but I get NA in the date.time column created.</p>
  
  <p>I have also tried getting rid of the date with:  </p>
  
  <pre><code>data_frame2_date_filter$Time &lt;- format(ymd_hms(data_frame2_date_filter$Time), "%H:%M:%S")
  
  atr_results$Time &lt;- parse_date_time(atr_results$Time, "HMS")
  atr_results$Time &lt;- times(strftime(atr_results$Time, format="%H:%M:%S"))
  </code></pre>
  
  <p>but these don't work either.</p>