https://herc.ws/board/topic/18887-help-converting-small-piece-of-code-to-hercules/

attendance_staylogin.c

#include "common/hercules.h"
#include "map/pc.h"
#include "map/npc.h"
#include "map/clif.h"
#include "common/memmgr.h"
#include "plugins/HPMHooking.h"
#include "common/HPMDataCheck.h"

HPExport struct hplugin_info pinfo = {
	"attendance_staylogin",
	SERVER_TYPE_MAP,
	"",
	HPM_VERSION,
};

int require_stay_seconds = 90; // change to 3600 as 1 hour

// Returns YYYYMMDD of now
int date_get_date(void)
{
	time_t t;
	struct tm * lt;
	t = time(NULL);
	lt = localtime(&t);

	return
		(lt->tm_year + 1900) * 10000 +
		(lt->tm_mon + 1) * 100 +
		(lt->tm_mday);
}

struct player_data {
	int unixtime_login;
};

//	trigger when login
static int pc_reg_received_post(int retVal, struct map_session_data *sd) {
	if (retVal == 0)
		return 0;
	struct player_data *ssd;
	CREATE(ssd, struct player_data, true);
	ssd->unixtime_login = (int)time(NULL);
	addToMSD(sd, ssd, 0, true);
	if (pc_readaccountreg(sd, script->add_variable("#Attendance_date")) != date_get_date()) {
		pc_setaccountreg(sd, script->add_variable("#Attendance_date"), date_get_date());
		pc_setaccountreg(sd, script->add_variable("#Attendance_staylogin"), 0);
		pc_setaccountreg(sd, script->add_variable("#Attendance_claimed"), 0);
	}
	return 1;
}

//	trigger when logout
static int map_quit_pre(struct map_session_data **sd) {
	struct player_data *ssd = getFromMSD(*sd, 0);
	if (pc_readaccountreg(*sd, script->add_variable("#Attendance_claimed")) == 0)
		pc_setaccountreg(*sd, script->add_variable("#Attendance_staylogin"), pc_readaccountreg(*sd, script->add_variable("#Attendance_staylogin")) + (int)time(NULL) - ssd->unixtime_login);
	return 0;
}

//	deny claim reward
static void clif_parse_attendance_reward_request_pre(int *fd, struct map_session_data **sd) {
	if ((*sd)->state.trading || pc_isdead(*sd) || pc_isvending(*sd))
		return;
	if ((*sd)->status.base_level < 75) {
		clif->messagecolor_self((*sd)->fd, COLOR_RED, "You must be at least level 75 before you qualify for Daily Attendance.");
		hookStop();
		return;
	}
	struct player_data *ssd = getFromMSD(*sd, 0);
	int var_staylogin = pc_readaccountreg(*sd, script->add_variable("#Attendance_staylogin"));
	if (var_staylogin + time(NULL) - ssd->unixtime_login < require_stay_seconds) {
		char tmp[CHAT_SIZE_MAX];
		safesnprintf(tmp, CHAT_SIZE_MAX, "You still need %d seconds to claim the reward", require_stay_seconds - (var_staylogin + (int)time(NULL) - ssd->unixtime_login));
		clif->messagecolor_self((*sd)->fd, COLOR_RED, tmp);
		hookStop();
	}
	return;
}

//	after collect reward, set variable
static void clif_parse_attendance_reward_request_post(int fd, struct map_session_data *sd) {
	pc_setaccountreg(sd, script->add_variable("#Attendance_claimed"), 1);
	return;
}


//	reset variable when server touch 12am
static int npc_event_do_clock_post(int retVal, int tid, int64 tick, int id, intptr_t data) {
	static struct tm ev_tm_b; // tracks previous execution time
	time_t clock = time(NULL);
	struct tm* t = localtime(&clock);

	if (t->tm_min != ev_tm_b.tm_min && t->tm_hour == 0 && t->tm_min == 0) {
		struct map_session_data *sd;
		struct player_data *ssd;
		struct s_mapiterator *iter = mapit->alloc(MAPIT_NORMAL, BL_PC);
		for (sd = (struct map_session_data*)mapit->first(iter); mapit->exists(iter); sd = (struct map_session_data*)mapit->next(iter)) {
			if ((ssd = getFromMSD(sd, 0))) {
				pc_setaccountreg(sd, script->add_variable("#Attendance_date"), date_get_date());
				pc_setaccountreg(sd, script->add_variable("#Attendance_staylogin"), 0);
				pc_setaccountreg(sd, script->add_variable("#Attendance_claimed"), 0);
				ssd->unixtime_login = 0;
			}
		}
		mapit->free(iter);
	}
	memcpy(&ev_tm_b,t,sizeof(ev_tm_b));
	return retVal;
}

HPExport void plugin_init (void) {
	addHookPost(pc, reg_received, pc_reg_received_post);
	addHookPre(map, quit, map_quit_pre);
	addHookPre(clif, pAttendanceRewardRequest, clif_parse_attendance_reward_request_pre);
	addHookPost(clif, pAttendanceRewardRequest, clif_parse_attendance_reward_request_post);
	addHookPost(npc, event_do_clock, npc_event_do_clock_post);
}