Respect system/user timezone in API requests (#2630)

* Respect system/user timezone in API requests

* Fall back to a known timezone if TZ is not set

Co-authored-by: Cristian Dominguez <cristiand391@users.noreply.github.com>

pkg/cmd/factory/http.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/cli/cli/api"
 	"github.com/cli/cli/internal/config"
@@ -12,6 +13,46 @@ import (
 	"github.com/cli/cli/pkg/iostreams"
 )
 
+var timezoneNames = map[int]string{
+	-39600: "Pacific/Niue",
+	-36000: "Pacific/Honolulu",
+	-34200: "Pacific/Marquesas",
+	-32400: "America/Anchorage",
+	-28800: "America/Los_Angeles",
+	-25200: "America/Chihuahua",
+	-21600: "America/Chicago",
+	-18000: "America/Bogota",
+	-14400: "America/Caracas",
+	-12600: "America/St_Johns",
+	-10800: "America/Argentina/Buenos_Aires",
+	-7200:  "Atlantic/South_Georgia",
+	-3600:  "Atlantic/Cape_Verde",
+	0:      "Europe/London",
+	3600:   "Europe/Amsterdam",
+	7200:   "Europe/Athens",
+	10800:  "Europe/Istanbul",
+	12600:  "Asia/Tehran",
+	14400:  "Asia/Dubai",
+	16200:  "Asia/Kabul",
+	18000:  "Asia/Tashkent",
+	19800:  "Asia/Kolkata",
+	20700:  "Asia/Kathmandu",
+	21600:  "Asia/Dhaka",
+	23400:  "Asia/Rangoon",
+	25200:  "Asia/Bangkok",
+	28800:  "Asia/Manila",
+	31500:  "Australia/Eucla",
+	32400:  "Asia/Tokyo",
+	34200:  "Australia/Darwin",
+	36000:  "Australia/Brisbane",
+	37800:  "Australia/Adelaide",
+	39600:  "Pacific/Guadalcanal",
+	43200:  "Pacific/Nauru",
+	46800:  "Pacific/Auckland",
+	49500:  "Pacific/Chatham",
+	50400:  "Pacific/Kiritimati",
+}
+
 // generic authenticated HTTP client for commands
 func NewHTTPClient(io *iostreams.IOStreams, cfg config.Config, appVersion string, setAccept bool) *http.Client {
 	var opts []api.ClientOption
@@ -29,6 +70,16 @@ func NewHTTPClient(io *iostreams.IOStreams, cfg config.Config, appVersion string
 			}
 			return "", nil
 		}),
+		api.AddHeaderFunc("Time-Zone", func(req *http.Request) (string, error) {
+			if req.Method != "GET" && req.Method != "HEAD" {
+				if time.Local.String() != "Local" {
+					return time.Local.String(), nil
+				}
+				_, offset := time.Now().Zone()
+				return timezoneNames[offset], nil
+			}
+			return "", nil
+		}),
 	)
 
 	if setAccept {