R: Correctly Writing and Converting Dates in UTC Format

I am trying to learn how to use the Reddit API (https://www.reddit.com/prefs/apps).

I registered for an account/API - I want to retrieve 100 comments containing the word "covid" posted between March-01-2020 and March-02-2020.

Using the documentation from the API (https://www.reddit.com/dev/api/), I ran the following R code.

First, I registered the API:

library(httr)
library(jsonlite)

response <- POST("https://www.reddit.com/api/v1/access_token",
                 authenticate('****', '***'),
                 user_agent("some_name"),
                 body = list(grant_type="password", 
                             username="aaaaaa", 
                             password="bbbbbbb"))

access_token_json <- rawToChar(response$content)
access_token_content <- fromJSON(access_token_json)
access_token <- access_token_content$access_token
access_token

url <- "https://oauth.reddit.com/LISTING" # try api/v1/me

authorization_bearer <- paste("Bearer ", access_token, sep="")
result <- GET(url, 
              user_agent("some_name"), 
              add_headers(Authorization = authorization_bearer))

Next, I tried to make a request:

# Set start and end times
start_time <- as.numeric(as.POSIXct("2020-03-01 16:52:00", tz = "UTC"))
end_time <- as.numeric(as.POSIXct("2020-03-02 13:52:00", tz = "UTC"))

# Set query parameters 
query_params <- list(
  limit = 100,
  q = "covid",
  #subreddit = "news", # 
  #author = "some_author", #
  after = start_time,
  before = end_time
)

# Make the API request 
response <- GET(url, query = query_params, add_headers(Authorization = authorization_header, `User-Agent` = user_agent_string))

# Extract the response 
response_json <- rawToChar(response$content)
response_content <- fromJSON(response_json)

# Extract the relevant fields 
final_result <- data.frame(
  title = response_content$data$children$data$title,
  subreddit = response_content$data$children$data$subreddit,
  author = response_content$data$children$data$author,
  created_utc = as.POSIXct(response_content$data$children$data$created_utc, origin = "1970-01-01", tz = "UTC"),
  permalink = paste0("https://www.reddit.com", response_content$data$children$data$permalink)
)

When I look at the results:

> head(final_result)
                                                                                   title          subreddit            author         created_utc
1 COVID-19 is a leading cause of death in children and young people in the United States            science thebelsnickle1991 2023-01-30 16:27:21
2                I thought Covid was a thing of the past.. double vaccinated wicked sick  mildlyinfuriating    Northeast4life 2023-02-19 00:52:03
3          ‘People aren’t taking this seriously’: experts say US Covid surge is big risk               news           ttkciar 2023-01-15 17:25:12

As we can see here, the dates are not between the specified dates.

I thought the problem is that maybe I am not converting the date properly, so I looked at the raw UTC dates :

> final_result$created_utc
  [1] 1675096041 1676767923 1673803512 1671022066 1674220458

But these dates do not seem to correspond to the dates I wanted in March 2020 (https://www.epochconverter.com/).

Am I not writing the dates correctly - can someone please show me how to fix this?

Thanks!

Try converting the start and end strings to their Unix timestamps with the as.character() function:

# Set start and end times
start_time <- as.character(as.POSIXct("2020-03-01 00:00:00", tz = "UTC"))
end_time <- as.character(as.POSIXct("2020-03-02 23:59:59", tz = "UTC"))